well it's happening in dailyPregnacy, so I'm guessing it's a problem in Aric's. Are you playing with the base version of my standalone version of Aric's Mod or the optional version? Any other mods installed?
I know with Aric's Mod it's good to delete the backup before applying the mod because you actually have to directly overwrite some of the main game files directly as part of the installation process. So if you don't delete the backup, it will just overwrite your changes with the original files you had before. My understanding is that if a mod has no such manually installed files for you to deal with, you shouldn't need to delete the backup, but it doesn't hurt to do so anyway.
Could you try a fresh install and tell me if this still happens?
For a fresh install: Just unzip the S4PGameFolderRMAM097 folder to a new location fresh from the .7z file and rename it S4PGameFolderRMAM097-test or similar. Then, rename your existing AricsExpansion folder in appdata/roaming/etc. to AricsExpansion-backup and copy AricsExpansion from the .7z file to your appdata/roaming/etc. in place of the one you renamed.
If you do that and open the game directly from the Strive.exe in the new S4PGameFolderRMAM097-test folder, and you still have these errors, then it's got to be a problem in my version. If the error doesn't occur anymore, then you can try copying your save over from AricsExpansion-backup to AricsExpansion and load it to see if the error reappears. If not, you're all set.
The pregnancy error persists in different versions of the game (regular and additional, with and without mods), I replayed several times with the renamed folder, following your instructions ...
**SCRIPT ERROR**: Invalid get index 'I117' (on base: 'Dictionary').
At: res://files/scripts/items.gd:1898:unequipitem() - Invalid get index 'I117' (on base: 'Dictionary').
Aric's Expansion v0.97
**SCRIPT ERROR**: Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
At: user://mods/AricsExpansion/scripts/aricsexpansion/expansion.gd:1772:dailyPregnancy() - Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
**SCRIPT ERROR**: Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
At: user://mods/AricsExpansion/scripts/aricsexpansion/expansion.gd:1772:dailyPregnancy() - Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
**SCRIPT ERROR**: Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
At: user://mods/AricsExpansion/scripts/aricsexpansion/expansion.gd:1772:dailyPregnancy() - Invalid get index 'back' (on base: 'Array'). Did you mean '.back()' or funcref(obj, "back") ?
**SCRIPT ERROR**: Invalid get index 'skin_cov' (on base: 'Reference (person.gd)').
At: res://files/scripts/characters/description.gd:402:getBabyDescription() - Invalid get index 'skin_cov' (on base: 'Reference (person.gd)').
**SCRIPT ERROR**: Invalid operands 'String' and 'Nil' in operator '+'.
At: res://files/scripts/Mansion.gd:3104:childbirth() - Invalid operands 'String' and 'Nil' in operator '+'.
You said "before installing any mod, I delete the backup, otherwise, after installation, errors appear in the mod panel", for which he asked you to try a fresh install without deleting the backup.
The errors you posted do not appear to be related to the mod panel in any discernible way, but instead seem to be standard Aric's mod gameplay errors found on the terminal window. I think there is a bit of a misunderstanding here.
Not sure when the next version with fixes will be out, Ralph would have to answer that. Though Strive's scripts are pretty easy to edit with a decent text editor, and many of those errors have solutions identified in either Aric's mod topic or on the Strive Discord (https://itch.io/t/284398/discord), which is a great place for fixing bugs fast.