So I'm back after a lot of canola-farm and lube-making-action. I managed to make my boring machines work more or less consistently again with version 25z. And sadly, it turns out the server still starts lagging when enabling them. I have no real clue why. I still think it's always when one of them has to generate a new chunk. A huge delay happens every minute or so. The boring machine has efficiency IV and Silk Touch, and WAILA says each action takes ~9 seconds, so it would fit, that one needs a new chunk every 144 seconds.
If I can help somehow by giving you more information, just let me know.
Thanks in advance - and thanks for taking some time and answering all the people here.
I love RoC and ReC.