I’d say it is fairly common. I have set up quite a few tubeless tyres and their ability to stay inflated over time when not being used seems to be utterly random to me.

I have a bike currently that I haven’t used for a few weeks that I know if I go back to now one tyre will still be at a pressure close to when I left it and the other will be pretty much flat.

I have re taped the rim, changed the tyre and tried two different types of sealant but it still needs pumping properly before use if I have left it without using it for more than a few days.

On other bikes I have had similar experiences as well. Wheels I have setup in identical ways with identical products have either held pressure or not over time with no real reason to point to either.

My point being in my experience I have accepted this as part of running tubeless and will always just need to pump up tyres after a period of not using them. Sorry I can’t offer any tips but if you find something that works please let me know.