Seeing HUGE disconnect between GSC and GA -- any ideas?

Hope everyone is doing well. I've run across a peculiar issue which I'm digging into, yet haven't found an answer for yet.

On Thursday and Friday, one of my sites unexpectedly received about 1/4 of its usual traffic as per Google Analytics. Knowing that there were of Google updates going on, and big volatility in the SERPs, I was initially concerned that the site was simply being punished by an update.

What is confusing to me is that GSC is indicating my usual number of clicks and impressions for those days, when I check the SERPs manually my rankings are as usual, and SEMRush doesn't indicate any dramatic negative movement. What is concerning is that my affiliate clickthrough is down significantly as well, correlated more with the low traffic than the clicks.

My thoughts turned to a potential hosting / loading error and time-out, which would cause a disconnect between folks clicking my articles on Google and never making it to the website (and thus never firing the GA JS code) but everything seems to be clean there. And while I have my support running diagnostics to look for hacks or re-directs, we haven't turned anything up yet.

I wanted to check in to see if anyone had ever seen such huge disparities between their GSC and GA? I'm talking a 4x difference between folks clicking and actual traffic. I know they record slightly different metrics and never match perfectly, but this is still way outside the realm of expected differences.

Would appreciate any insight or help here -- thanks!