win 8.1 x 64 reaper 5.32 rc 1
(confirmed in minimal project file as well as my licecap)
1- create a project with some envelopes on a track
2- NOTE: envelope activity at marker 7 in licecap
3- change tempo
4- undo changed tempo to revert to previous tempo.
5- BUG: envelopes have irrevocably shifted to changed tempo position.
NOTE: envelope activity no longer aligns with marker 7, where it is expected.
NOTE: this cannot be reverted with an undo - they are stuck there and you have to go back to a reaper backup file if you're lucky enough to have one.
NOTE: in step 4, if you manually change the tempo back to what it was before, this bug does not occur. the bug appears to be in the undo step.
another example, more minimal. note how envelope objects at first only exist between markers 1 and 3: after tempo change undo, they exist between 1 and 4.