There aren’t many properties that could be changed and have impacts on the tween though.
For my gui object, the only properties I did change and do matter were only the Position, Size, and AnchorPoint, so there isn’t really anything special with my gui object.
Maybe you can try and create a new gui object and type a new script on it to see if it still happens the same way. But anyway, I don’t think I can help you anymore, I apologize.
(Edit: Or maybe try doing the entire thing even on a new roblox place)
Are you tweening this GUI on the server or the client? From your script, I would guess the server. Tweens from the server don’t replicate well, but if this is the client, the only other thing I can really think of is your current client memory usage.