In the John Mueller hangout on 08/13/2021, a webmaster was concerned regarding a number of 500 errors showing up in Google Search Console.
John explained that there aren’t any real thresholds on this. He also explained that Google will retry these 5xx errors over and over again and they will remain indexed.
After several tries, if Google determines that these pages really are still gone, they will drop them.
These are the effects you will see for 500 errors. If there’s more than a 1 percent issue with these errors—compared to the number of pages on your site—you will want to examine your site for major issues just in case something is broken.
The webmaster was also concerned about 504 errors, and whether or not having a 200 error read at exactly the same time—on that same URL as the 500 error—is a problem.
The webmaster asks this question at approximately the 13:46 mark in the hangout.