#IfExist is marked as a "Expensive Parser Function Call", there is a hard limit of 100 of these in a page.
https://en.wikipedia.org/wiki/Help:Template_limits#Expensive_parser_function_calls
Now, I *can* increase this limit, however I've watched the PHP-FPM pool for just the wiki use up 40-50% of the web server's CPU with the current limits in place, so I'm not sure that's a great idea... I could try to raise the limit slightly as a test, but with the understanding that if it spikes CPU usage too much I'll have to drop it back down.
Edit to add, this is a 8 core 3.2 GHz CPU, not like a RPi, 40-50% of this CPU is an insane amount, and the wiki has its own dedicated FPM pool.