I also had Smart Scan suddenly set on a monthly schedule I didn’t ask for.

I disabled it through Settings → Protection → Smart Scan → set it to Run Manually.

If you set it to Monthly there, you can then change the date and time when it will run.

So maybe delete the Smart Scan you created and change the date and time of the automatically set one to your liking.

This should result in 1 (one) monthly Smart Scan, I would guess.

If that is what you already did, and despite that Avast runs a secondary Smart Scan whenever it pleases that isn’t configurable somewhere in settings, then yes wait until they hopefully fix it.

I will say this though: If you have a monthly full scan scheduled, running a scheduled Smart Scan before it is useless. As I understand it, it basically is a subset of the full scan, so it would be wholly redundant.

You might also consider not running any scheduled scans at all, and only occasionally scan manually. Unless you regularly disable Avast for whatever reason. If it is always running in the background, it should have checked every file as it was created or modified. And if the virus definitions have changed to include a file after it was already downloaded and stored, it will flag/block it whenever a program tries to access it.