Image of the changed toolbar buttons position
After the upgrade to mw1.19, the custom toolbar keeps switching positions from appearing correctly at the end of the regular toolbar to splitting the regular edit toolbar into two parts. Also the revised code for custom toolbar buttons doesn't work for me.
This happens on Wikimedia Commons and Wikipedia and most importantly on Wikisource, where most of my editing is done.
Recently, the positional change became more frequent, and I copied the source page code of both conditions, and created a .jpg image of both as they appear in Wikisource.