While inspecting this problem https://project-gc.com/forum/read?8,20085 which happens occasionally. I found something potentially important.

This checker is database intensive but it should run normally fast enough. At some times the checker displays error and I was debugging it more deeply when I found that the checker will keep running after the error message.

This was a succesfull run:
Got profile name, arisoft
Target:Akaa, 12caches, CPU time 0.066236561s, Real time 3s
Target:Asikkala, 11caches, CPU time 0.067935707s, Real time 4s
Target:Askola, 10caches, CPU time 0.069259963s, Real time 5s
....
Target:Rautjärvi, 14caches, CPU time 0.221535804s, Real time 73s
Target:Riihimäki, 10caches, CPU time 0.225073671s, Real time 74s
Target:Ruokolahti, 10caches, CPU time 0.231784346s, Real time 75s

This was an unsuccesfull run:
Got profile name, grateful cacher
Target:, 10caches, CPU time 0.063781417s, Real time 4s
Target:Ada County (ID), 16caches, CPU time 0.065383221s, Real time 6s
Target:Adams County (PA), 12caches, CPU time 0.066967627s, Real time 8s
....
Target:Delta County (MI), 12caches, CPU time 0.153566129s, Real time 98s
Target:Deschutes County (OR), 12caches, CPU time 0.155297352s, Real time 99s
Target:District of Columbia (DC), 11caches, CPU time 0.156759969s, Real time 100s <--- error displayed
Target:Douglas County (GA), 12caches, CPU time 0.158353155s, Real time 101s
Target:Douglas County (NV), 11caches, CPU time 0.160056218s, Real time 102s
....
Target:Humboldt County (NV), 11caches, CPU time 0.204044803s, Real time 143s
Target:Jackson County (MO), 10caches, CPU time 0.205374969s, Real time 144s
Target:Jackson County (OR), 10caches, CPU time 0.206879322s, Real time 145s

The checker got results after 145 seconds in real time and 0,2 seconds in CPU time.
When the checker was run 100 seconds the UI displayed this error

Queueing for slot, paying members are prioritized.
Current position in queue: 0
Using token: 75aad867b7eb7a30686fbc1bfa8907e9
Running checker, this might take up to 60 seconds. Countdown: 0
Retrieving additional information.
Error
Execution time (s)
Peak memory usage (kB)
Error message Caught exception
Execution status