Currently in game, rolling a natural 1 on any check automatically fails you without taking into consideration any bonuses or even the original DC - Larian have confirmed that this is their change and is working as they intend. All we can do is bombard them with regular feedback to tell them that natural 1s are not auto-fails on skill and ability checks, or saving throws, and should only apply to attack rolls (and the very specific death saving throw), and to ask them to change their mind about this.
I don't play TT 5e, but page 242 of the DMG addresses the issue of saves and ability checks, discussing not only critical success/failure (extreme outcomes), but also partial success/failure, and marginal success/failure. The notion is to encourage DMs to consider a continuum of outcomes and complications. rather than always apply simple pass/fail absolutism, which is not always a satisfying experience for players.
So whatever Larian have decided to implement for ability checks and saves, it is not a "bug", but a development choice. You can still tell them you don't like it ( with or without coherent reasoning ), but it isn't wrong according to 5e DMG.
Personally, I haven't found it matters much. The game plays enjoyably well, regardless of how the die falls.
