The likely reason that the brushes cause a crash is because 5.1 beta 1 has a regression where brushes saved or created in that version have buggy metadata that are unable to be read in other versions.
You can observe this by opening a .kpp in Krita 5.1 beta 1 and checking for escape codes in Image → Properties → Annotation. Escape codes such as < and > aren’t supposed to be there and suggest that the brush should be remade in a non-bugged Krita version (like the current Krita Plus build or the upcoming beta 2). EDIT: Brushes can now be converted to normal versions by using a plugin linked later in this thread.
Might be worth noting that this issue doesn’t affect brush backups that were made in a version without that regression, so you can possibly revert to a particular backup if the brush only has small tweaks made in beta 1.
Oh noooo! Please someone tell me that there’s an easier way! I’ve made or edited quite a few brushes in beta1, aaarrrgh! Already noticed that my brushes seemed to crash the nightlies or even 5.0.6. - now I know…
Can the newer versions not simply ignore those codes? How can something like this even happen…? Not amused…
Ah, that’d be really a godsend! And btw. thanks for posting the info (both about the bug and a possible solution) - I was just a little bit frustrated.
I have already encountered this problem, that’s why there are 2 different packs one for 5.1Beta and one for older versions. Newer brushes crush older Krita.
The brushes made before 5.1 beta (in 5.0.6 for example, or in nightly versions before the change in metadata) should be working just fine in 5.1 beta 2 and future versions.
This was a bug, thankfully discovered before final release.
I will make the script asap (Also will try to ensure Krita won’t crash even encountering them in the wild, but I don’t think adding code to read them would be beneficial, it would be mostly maintenance cost, better to just convert all of the presets to the proper version and drop those that crash/can’t be loaded).