It appears to be affecting a sub-set of users, but of course it is annoying if you are one of those users.
From what I can see from the reports so far it's an issue with updating particular software, or softwares.
It's only affecting Health Check,
only if you have CCleaner Pro.
and only if you have a particular software, or softwares, to update.
(Your Antivirus/Firewall rules may or may not also be involved, but it doesn't seem to be a main factor).
The obvious fix will be to remove the offending software(s) from the list of those to be updated - once you know what software that is.
I have no idea just what software that might be, but presumably it's one of the ones added to the updating list in v6.21.
It would take testing to find, or for affected users to report what software Tools>Software Updater was finding for them to see if something common could be spotted.
(I will note that the lists of what softwares to update are slightly different in Health Check than the seperate Software Updater, that might help the devs track it down).
So it's a combination of at least 3 factors, one of which is dependent on what other software the user has on their machine and if it's up to date or not.
Such combinations can and do get missed in testing.
There is only limited testing time for any release, which means that you can't test every single possibly combination only the more common ones.
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If you are affected then you can try using Tools>Software Updater to update what it finds a couple at a time.
Others have reported that fixes the issue for them.
If you don't want to try that, or if it doesn't work for you, then I suggest that for the moment you use Custom Clean instead of Health Check.