MacOs lost the window size configuration from a long time...

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

You are probably aware of this, but just in case: you won't get the custom size if you are on an already open window. For example, if you are in folder A, and have B inside, and open it in the existing window, it will remain in the same size.

But control-option click B and choose Open in New Window, and the new window will use the size associated with B.

The settings are per folder, not overall.

Changes that you make will apply to a new folder that you create, or that you have not opened before in the Finder, but will not be applied retroactively to other folders.

Case in point:

Open folder A, and set it with a large window and Icon View

Close folder A

Open folder B, and set it to small window in List View

Open folder A - it will still be as you set it above.