Also seems to happen when I'm close to my Personal safe. This safe was spawned.
It seems other machinery is fine. I have not tested other generators.
More specific:
It drops the FPS only when I walk within (maybe) 5blocks of the closest solarpanel and the safe, but not every time. (night/day is the same)
The FPS goes back to normal once I move away from the panels (maybe 5 blocks away from the nearest panel)
Using a freshly modded minecraft 1.8 following the instructions on the wiki. Installed all mods and patches/fixes in the specified order. No other mods are installed.
edit: Using Indcraft 1.15
Update:
Restarted my minecraft, lags are now gone. Will report back if they reappear.
update2:
Yep, happens after a while again after every restart. Always close to the solar panels when it happens for me.