In the crafting menu, when hovering over some recipes (but not all) there is a severe FPS drop that lasts until
the user is no longer hovering over that recipe.

I cannot reproduce in base game and each of the respective mods are fine on their own. However when
put together I can reproduce this error. This is the smallest reproducible build I could find with bob/angels
showing the fps drop.

Example Video: https://www.dropbox.com/s/p6t2ptg2k13871y/factorio%20bug.mp4?dl=0
Note: video was taken in a freshly generated sandbox scenario world (default settings used)

PC Specs

Windows 10 x64 Pro
AMD FX-8350 /w 16 GB Ram
Nvidia Geforce GTX 1660 super
1TB WD Blue SSD

Mod Versions

Factorio Version: 0.17.79(build 47865, win64, steam)
Angel's Petro Chemical Processing v0.8.6
Angel's Refining v0.10.14
Bob's Functions Library v0.17.5
Bob's Metals, Chemicals and Intermediates v0.14.13

This report was also filed with Angels Mods here: https://forums.factorio.com/viewtopic.php?p=474125#p474125

I think it's because it's a fairly complex recipe, it's trying to calculate through a lot of intermediate stages.

I actually went through my own mods a few months ago and at certain points set things to not be decomposable (probably the wrong word), but the function basically means... if you have oxygen in a recipe, it's not going to try and tell you that you need air or water to make it, and some of the recipes were giving really strange results, it was trying to break some of them down into units of air, water, seedlings and ores. So most of the decomposition limits were set on things you normally cant craft by hand, like metal plates and wood (can be made in a greenhouse), to try and solve this kind of issue.

It looks like those complex recipes you're pointing at there are from Angel's mods.