I also in general use document editing in the browser on mobile only in very rare conditions. Where best experience anyway (no matter which office application) is on the computer within native application, being in the browser makes it already worse and then on mobile another layer of annoyance. And further consider that the general feature set of google docs or Office 365 is already below Collabora in my opinion.
However, that said, I would never ever consider my use cases being the right way to work. I am sure there are very good reasons for such use cases. And just because of that obviously it should work in a stable manner.
But I learned, that if something does not work, it should be communicated to the right people/location/forum/⌠even when I think I cannot be the only one with that issue. I experienced many times, that everyone thought that and nobody communicated the problem. I am not sure if in the first place when sheets was unusable for weeks, the problem has been communicated. - I am using NextCloud only in a small environment, but cannot remember sheets being unusable for weeks. But consider doing spreadsheet on mobile is a very rare use case here.