This is the fix. I think the issue was that we did two things at the same time:
* changed the text in editor (renaming) 
* lazily retrieve find usages results from `Compiler.Service`
I'm not sure, but it seems that `Compiler.Service` starts to invalidate itself when it detects code changes and the find usages `seq` become non valid.
The exception is as follows:
```
[Rename Refactoring] Error System.InvalidOperationException: Enumeration has not started. Call MoveNext.
   at Microsoft.FSharp.Collections.IEnumerator.notStarted[a]()
   at Microsoft.FSharp.Collections.IEnumerator.MapEnumerator`1.GetCurrent()
   at Microsoft.FSharp.Collections.IEnumerator.MapEnumerator`1.System-Collections-Generic-IEnumerator`1-get_Current()
   at <StartupCode$FSharpVSPowerTools-Core>.$Utils.For@77-2.Invoke(Unit unitVar0) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 78
   at FSharpVSPowerTools.MaybeBuilder.Delay[T](FSharpFunc`2 f) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 38
   at <StartupCode$FSharpVSPowerTools-Core>.$Utils.For@74.Invoke(IEnumerator`1 enum) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 75
   at FSharpVSPowerTools.MaybeBuilder.Using[T,a](T resource, FSharpFunc`2 body) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 56
   at FSharpVSPowerTools.MaybeBuilder.For[T](IEnumerable`1 sequence, FSharpFunc`2 body) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 74
   at <StartupCode$FSharpVSPowerTools-Logic>.$RenameCommandFilter.clo@63-32.Invoke(Document _arg4) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Logic\RenameCommandFilter.fs:line 63
   at <StartupCode$FSharpVSPowerTools-Logic>.$RenameCommandFilter.clo@62-31.Invoke(Unit unitVar) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Logic\RenameCommandFilter.fs:line 62
   at FSharpVSPowerTools.MaybeBuilder.Delay[T](FSharpFunc`2 f) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Core\Utils.fs:line 38
   at FSharpVSPowerTools.Refactoring.RenameCommandFilter.rename(String oldText, String newText, IEnumerable`1 foundUsages) in L:\git\FSharpVSPowerTools\src\FSharpVSPowerTools.Logic\RenameCommandFilter.fs:line 61 occurs while renaming symbols.
```