I've had two sporadic problems for years throughout different versions and they are very highly frustrating since they interfere with successful automation (TaskScheduler).
About 75% of the time, AmiBroker will import AmiQuote downloads at its normal, fast speed (Yahoo or Tiingo historical data), but the other 25% of time it will slow to crawl such that even 8 hours later, it will still be importing the tickers! There's no real fix for this as it seems to be hit or miss, but rebooting will usually clear up the slow speed, but not always. I've had it happen several times in a row.
The other problem is sometimes a dialog box popping up saying "This application is not responding" or some such and completely pauses the import. I have traced it to AmiBroker as the specific source and not AmiBroker. It is a separate problem from the slow importing, but may be tangentially related.
The above two happen both in a bare metal Windows VirtualBox VM with no anti-virus, Defender, etc. as well as on a regular Windows desktop with all the usual frills. There is nothing I can detect as a trigger pattern.