Thanks for your report.
1) Really odd bug - first instance of this your report. Would you be able to test this again to confirm it happens all the time.
2) This is a known bug. We mostly addressed it in the last patch, and the new new patch will make even better - this OOS should be gone for good soon.
3) might take us a while to fix - meanwhile it`s best not to position Archers and Trebuchets together.