i cannot open the engineers manual. i tried everything, putting off the item in the offhand, left and right click and so on...

Please read the contributing guidelines, edit the issue to give the required information and post a comment here when you are done (edits don't cause notifications).

do you have CTM mod loaded? if so it crates an error with some of the blocks. I had this issue and removing CTM fixed the issue. you may need to try a different version of CTM if you need it.

Closing this, due to lack of information provided in favor of a better documented issue linked above.