diff --git a/fuzzers/FRET/src/systemstate/mutators.rs b/fuzzers/FRET/src/systemstate/mutators.rs
index f081ab1b06..bd62c2192f 100644
--- a/fuzzers/FRET/src/systemstate/mutators.rs
+++ b/fuzzers/FRET/src/systemstate/mutators.rs
@@ -14,6 +14,7 @@ use libafl::prelude::Corpus;
 use libafl::prelude::UsesInput;
 use core::marker::PhantomData;
 use std::cmp::max;
+use std::cmp::min;
 use libafl::state::HasCorpus;
 use libafl::state::HasSolutions;
 use libafl::state::HasRand;
@@ -68,8 +69,6 @@ where
             target_bytes = input.bytes().to_vec();
         }
 
-        let mut target_tick = 0;
-
         // produce a slice of absolute interrupt times
         let mut interrupt_offsets : [u32; 32] = [0u32; 32];
         let mut num_interrupts : usize = 0;
@@ -92,8 +91,11 @@ where
             }
         }
 
+        println!("Vor Mutator: {:?}", interrupt_offsets[0..num_interrupts].to_vec());
+        // let num_i = min(target_bytes.len() / 4, DO_NUM_INTERRUPT);
+        let mut suffix = target_bytes.split_off(4 * num_interrupts);
         let mut prefix : Vec<[u8; 4]> = vec![];
-        let mut suffix : Vec<u8> = vec![];
+        // let mut suffix : Vec<u8> = vec![];
         // #[cfg(feature = "feed_systemtrace")]
         {
             let tmp = _input.metadata().get::<FreeRTOSSystemStateMetadata>();
@@ -110,26 +112,78 @@ where
                 let m = interrupt_offsets[0..num_interrupts].iter().any(|x| (curr.start_tick..curr.end_tick).contains(&(*x as u64)));
                 if m {
                     marks.push((curr, i, 1));
-                    // println!("1: {}",curr.current_task.task_name);
+                    println!("1: {}",curr.current_task.task_name);
                 } else if last_m {
                     marks.push((curr, i, 2));
-                    // println!("2: {}",curr.current_task.task_name);
+                    println!("2: {}",curr.current_task.task_name);
                 } else {
                     marks.push((curr, i, 0));
                 }
                 last_m = m;
             }
-            let untouched : Vec<u32> = marks.iter().filter_map(
-                |x| if x.2 == 0 {
-                    Some(x.0.start_tick.try_into().expect("ticks > u32"))
-                } else {
-                    None
-                }
-            ).collect();
-            let mut numbers : Vec<u32> = vec![];
             for i in 0..num_interrupts {
-                numbers.push(myrand.choose(untouched.clone().into_iter()).try_into().expect("ticks > u32"));
+                // bounds based on minimum inter-arrival time
+                let mut lb = 0;
+                let mut ub : u32 = marks[marks.len()-1].0.end_tick.try_into().expect("ticks > u32");
+                if i > 0 {
+                    lb = interrupt_offsets[i-1]+MINIMUM_INTER_ARRIVAL_TIME;
+                }
+                if i < num_interrupts-1 {
+                    ub = interrupt_offsets[i+1]-MINIMUM_INTER_ARRIVAL_TIME;
+                }
+                // get old hit and handler
+                let old_hit = marks.iter().filter(
+                    |x| x.0.start_tick < (interrupt_offsets[i] as u64) && (interrupt_offsets[i] as u64) < x.0.end_tick
+                ).next();
+                let old_handler = match old_hit {
+                    Some(s) => if s.1 < num_interrupts-1 && s.1 < marks.len()-1 {
+                        Some(marks[s.1+1])
+                    } else {None},
+                    None => None
+                };
+                // find reachable alternatives
+                let alternatives : Vec<_> = marks.iter().filter(|x|
+                    (
+                    x.0.start_tick < (lb as u64) && (lb as u64) < x.0.end_tick
+                    || x.0.start_tick < (ub as u64) && (ub as u64) < x.0.end_tick )
+                ).collect();
+                // in cases there are no alternatives
+                if alternatives.len() == 0 {
+                    if old_hit.is_none() {
+                        // choose something random
+                        let untouched : Vec<_> = marks.iter().filter(
+                            |x| x.2 == 0
+                        ).collect();
+                        let tmp = interrupt_offsets[i];
+                        let choice = myrand.choose(untouched);
+                        interrupt_offsets[i] = myrand.between(choice.0.start_tick, choice.0.end_tick)
+                            .try_into().expect("tick > u32");
+                        // println!("no alternatives, choose random i: {} {} -> {}",i,tmp,interrupt_offsets[i]);
+                        continue;
+                    } else {
+                        // do nothing
+                        // println!("no alternatives, do nothing i: {} {}",i,interrupt_offsets[i]);
+                        continue;
+                    }
+                }
+                let replacement = myrand.choose(alternatives);
+                if (old_hit.map_or(false, |x| x == replacement)) {
+                    // use the old value
+                    // println!("chose old value, do nothing i: {} {}",i,interrupt_offsets[i]);
+                    continue;
+                } else {
+                    let extra = if (old_hit.map_or(false, |x| x.1 < replacement.1)) {
+                        // move futher back, respect old_handler
+                        old_handler.map_or(0, |x| x.0.end_tick - x.0.start_tick)
+                    } else { 0 };
+                    let tmp = interrupt_offsets[i];
+                    interrupt_offsets[i] = (myrand.between(replacement.0.start_tick,
+                        replacement.0.end_tick) + extra).try_into().expect("ticks > u32");
+                    // println!("chose new alternative, i: {} {} -> {}",i,tmp, interrupt_offsets[i]);
+                }
             }
+            // println!("Mutator: {:?}", interrupt_offsets[0..num_interrupts].to_vec());
+            let mut numbers : Vec<u32> = interrupt_offsets[0..num_interrupts].to_vec();
             numbers.sort();
             let mut start : u32 = 0;
             for i in 0..numbers.len() {
@@ -140,7 +194,6 @@ where
             for i in 0..numbers.len() {
                 prefix.push(u32::to_le_bytes(numbers[i]));
             }
-            suffix = target_bytes[4*num_interrupts..].to_vec();
         }
         // #[cfg(feature = "sched_state")]
         // {