Drawing in warp block is shown on screen in V6 beta

Please fill out these questions for all feature requests and bug reports. If you're requesting a feature, please let us know why this feature is important or useful, not just what it should do.
Thanks!

  1. What browsers show this problem? Firefox & Chrome
  2. Please share an example project (if possible). https://snap.berkeley.edu/snapsource/dev/snap.html#present:Username=lowclouds&ProjectName=AODemo-in-v6
  3. Describes the steps to reproduce this issue. Start project, Click on small switchplate sprite near top middle.
  4. What does Snap! currently do? Watch lower right corner where sprite costumes are being created on the fly. You see random bits of costumes drawn on the stage, and at the end, there are usually bits left over.
  5. What should Snap! do instead? This is all done in 'warp' code, so none of it should be visible, and, more importantly, there shouldn't be bits left on the stage at the end.

Is this bug a security concern? If so, please do not post security concerns directly to the forum. Please email us at contact@snap.berkeley.edu. Thank you!

thanks for this report. Can you narrow it down a little more, I'd like to investigate...

Yes, sorry. I modified the library function 'costume from text..', my version is in 'generate costumes for ....' in the Looks section. This creates three new costumes for a cloned sprite, the ones that nest inside the outer sprite. I initially had problems with the costumes overwriting each other until I wrapped all the innards. (This still occasionally occurs in Chrome.) But the random blinking of the costumes on the stage remains as well as occasional leftover pen drawing.
This sprite creation occurs during the running of the project as each new state is entered the first time, and since the 'states' are just function blocks, I don't want to generate the costumes ahead of time.

thanks! That helps me narrow it down...