So is programmer textures getting fixed? Everything reporting that is getting closed as a duplicate of this, which is closed as works-as-intended, when programmers textures is obviously not intended to mess up chests.
Read the server setup instructions on minecraft.net. You can't just double-click the file.
Apparently not fixed, confirmed in 1.14.1
I've gotten this quite consistently, try spawning a bunch of Pillagers with a command block on repeating and killing them with /kill @e[type=pillager]. Then start a raid, or just summon more, neither will result in a banner.
I just had this happen trying to make a raid farm in my creative test world. I have a "village" about 30 blocks underground, so the Vex can't get to it. A trader spawned (I don't know if he spawned to me or to the "village", though). I killed one of the llamas and this happened. Maybe the "run back to village" and "panic because the llama was hit" speed multipliers stack?
Ah, yeah, that's it.