There have been several posts about the battery on the XPS 15 restricting the touchpad so that the physical touchpad buttons stop working.

I started having the same problem recently with my XPS 15 7590 after a couple of years of use. It didn't happen at once. Instead it was a gradual restriction that got worse over several months before it became really difficult to do a left mouse click. The soft touch still worked, but I must admit I preferred the physical click.

On close inspection, it seems there are two problems, neither of which Dell have owned up to (I had a long call with them today).

Firstly a design issue in my opinion, in that the gap between the underside of the touchpad and the battery is very small and very critical. Any swelling at all of the battery causes it to press against the underside of the touchpad and stop the buttons working. The touchpad actually requires a good millimeter or so to be free between it and the battery so that when you press the touchpad, the bottom of it has some room to move.

This was actually solved quite easily. I just installed some thin M2 nylon washers on all the screw holes under the battery. This has the effect of lifting the battery up slightly and gives the touchpad some more room underneath. It doesn't compromise any airflow and may actually improve it, so I would highly recommend this as it's a cheap fix and definitely solves the problem. Only use nylon washers in case you drop one inside your laptop. You can get them online for about a quid.

Then there's the battery itself. Looking closely at my battery, I can't see any visible swelling, so it may just be an imperceptible amount. LiPo batteries are prone to swelling if they overheat (the gel electrolyte emits gases that cause the swelling). When this happens you should replace the battery, however the battery management electronics is supposed to prevent overheating and overcharging, so it sounds like there's could be a longer term battery management problem. Basically there shouldn't be any swelling under normal use.

Also I recommend keeping the fans and heatsink on the laptop free of fluff as it does build up (I remove the fans on mine every few months and give them and the heatsink fins a careful vacuuming).

Finally I recommend installing the Dell Power Manager app (free from the Microsoft Store) as that allows you to modify the charging and cooling parameters to reduce the maximum charge from 100% and run the fans for more active cooling than would otherwise occur. Obviously charging less and cooling more will all help with eliminating battery swelling, but will give you shorter use times on each charge. I suggest playing with the settings until you come up with something that works for you.

I do like my XPS 15. I think it's probably the best laptop on the market and hope that Dell acknowledge these small niggles to help make it even better in the future.