I found the issue, the fieldEditor configuration caused this:
//% x.fieldEditor="gridpicker" x.fieldOptions.columns=2
I have seen this configuration in various examples including in the forum: Servo-write block creation
Removed it for now.
A great improvement to MakeCode would be a list of documentation-based errors like this and not only code-errors.
The playground did help speed things up a lot.
Since the extension uses additional hardware I’ve been using the offline version of MakeCode, in which I didn’t find a GitHub integration, however, for UI issues this was indeed redundant.
Is there an API call I can put in my GitHub workflow to invalidate the cache or is this only possible via a button in MakeCode itself?