Have you asked for help in discord?

NO

Describe your desired feature.

1.18 Synthetic too laggy
latest.log
1.20 doesn't get stuck
latest.log

Yeah this type of issues is why ASK ON DISCORD is the first advice.

Either describe the issue in details here or go to discord and explain!

this issue will be closed unless one of the above is done in timely manner

this means nothing to me.

try using words and describe the problem.

try only with IPN and the mod in question

post link to the mod that you think causes the problem.

1.18 Synthesis once, card twice

1.18 added REI , More sluggish

Version 1.20, 9 groups, one group at a time, 1 second put in, a few seconds synthesized

1.18, click on the left item to synthesize,With REI,Just put it in, 64, synthesis takes one minute,

Click on the item card below for a few seconds to put it in, click on the synthesis card for one minute, and then hold it for a few more seconds to synthesize

Suspected to be a problem with REImod