cachebuster storm

Looks like about a day ago this started spamming the error below. I’ve found it only does this when “WP Super Cache” is enabled. The strange thing is that my cache plugin was last updated 4 months ago, and I’ve been using these 2 together for years. No other changes to the site.

I’ve went through purged and rebuilt the wp super cache ‘cache’ with autoptimize disabled, then re-enabled and that doesn’t seem to have helped.

Right now I have left autoptimize disabled to keep the website up, otherwise this will generate a error 500 for our users.

Error output from access.log:

2607:f298:5:102f:: – – [17/Apr/2019:04:47:57 -0700] “GET /?ao_speedup_cachebuster=73497 HTTP/1.1” 200 32176 “https://www.hiddenoak.org/?ao_speedup_cachebuster=73497” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f::- – [17/Apr/2019:04:47:58 -0700] “GET /?ao_speedup_cachebuster=91153 HTTP/1.1” 200 32176 “https://www.hiddenoak.org/?ao_speedup_cachebuster=91153” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f:: – – [17/Apr/2019:04:48:04 -0700] “GET /?ao_speedup_cachebuster=67778 HTTP/1.1” 500 908 “https://www.hiddenoak.org/?ao_speedup_cachebuster=67778” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f:: – – [17/Apr/2019:04:48:05 -0700] “GET /?ao_speedup_cachebuster=21176 HTTP/1.1” 500 1029 “https://www.hiddenoak.org/?ao_speedup_cachebuster=21176” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f:: – – [17/Apr/2019:04:47:56 -0700] “GET /?ao_speedup_cachebuster=78552 HTTP/1.1” 500 31998 “https://www.hiddenoak.org/?ao_speedup_cachebuster=78552” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f::- – [17/Apr/2019:04:47:55 -0700] “GET /?ao_speedup_cachebuster=41075 HTTP/1.1” 500 32120 “https://www.hiddenoak.org/?ao_speedup_cachebuster=41075” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f::- – [17/Apr/2019:04:47:50 -0700] “GET /?ao_speedup_cachebuster=97780 HTTP/1.1” 500 32119 “https://www.hiddenoak.org/?ao_speedup_cachebuster=97780” “WordPress/5.1.1; https://www.hiddenoak.org”
2607:f298:5:102f:: – – [17/Apr/2019:04:48:07 -0700] “GET /?ao_speedup_cachebuster=2165 HTTP/1.1” 500 908 “https://www.hiddenoak.org/?ao_speedup_cachebuster=2165” “WordPress/5.1.1; https://www.hiddenoak.org”

The page I need help with: [log in to see the link]