Yes, it's a bug in v5.69 and as said above it will be fixed in the next CCleaner update.
It's a problem with 'leaking' device context handles, as you say that you are not a newbie to software user then you will probably know that 'leak' means that the longer the programme is open the more of the CPU it will want to use.
Closing the programme means it is no longer trying to hog the CPU.
This is why with normal use most users are not even aware that there is an issue, they open CCleaner, clean, and close CCleaner - the leak does not have time to affect anything noticably.
Only those who leave CCleaner open for longer times notice it, because the programme is open for longer it has time to hog the CPU.
In your particular case you are regularly wiping free space on 3 drives and that is not normal usage, (Wipe Free Space is not meant to be used like that), and that will mean that you have CCleaner open for longer than it would be in normal usage.
So it then becomes a race between can CCleaner finish wiping your 3 dives before the leak causes your CPU to top out, from what you describe then it is finishing the wipes but then because of the leak it has no more CPU resources to do anything else.
In that circumstance force closing CCleaner (by task manage or a restart) frees up the CPU again.
I suggest that if you realy insist on continuing to wipe all 3 of your drives with each run of CCleaner, which is your choice to make, then you stop wiping them until the next CCleaner update fixes the context handle leak. For now untick Wipe Free Space and just do the cleaning without the wiping of free space.
(Alternatively wipe one at once, closing and reopening CCleaner between each one).
Once the leak is fixed in the next update then you can go back to wiping free space every time if you want to. (But it's not necessary).
PS. While SSDs can stand many more rewrites than they used to do in the early days they still have a limit on how many times they can be written to, it's just a much bigger limit than the early SSDs had.