Have all these prints been sliced at the same time? (Like on the same version of the slicer)
I had an issue on my filament printer where I thought it was messing up, so I tried a few different prints to make sure and it was still failing. But it turned out that it was caused by a buggy Cura update
You can buy galvanised steel water butts. I don't know what their quality is like as I haven't been able to get one yet, but when I get a chance to install a water butt, it's what I plan to use.