Gates do not seem to properly activate/deactivate redstone signals when changing state. Please see gif for example.

https://i.imgur.com/FnyGRgW.gif

Buildcraft version:
buildcraft-7.99.13-pre10.jar commit a0000f7

Forge version:
forge-1.12.2-14.23.1.2566-universal.jar

Link to crashreport or log (on pastebin or gist, please don't put the entire log here) :
Singleplayer/multiplayer: Both

Additional information:

This should now be fixed in https://www.mod-buildcraft.com/buildcraft-79913-alpha-buildcraft-79982-alpha-buildcraftcompat-79913-alpha.html