Chopped logs don't give item drops, excluding the chopped log that the player last hit. For example, the tree in the screenshot is 6 logs tall, but only drops 3 logs when cut at the bottom.

Minecraft: 1.18.1
Forge: 39.0.59
Mods: TreeChop-1.18.1-0.15.5

Fixed in 0.15.6

Thanks for reporting, I'll get it fixed