Odd slicing problem with new 2.8.1 brim-thickness draft shield
I have a fairly simple model that requires internal supports. I'm printing it in PETG on a FFCP2 IDEX machine with PVA supports. the print keeps failing very early in the print when the PVA extruder collides with the latest draft shield layer put down by the PETG extruder. Looking at the slicer output, I see there is a draft shield layer where half the draft shield is printed in PVA and the other half in PETG - that doesn't look right.
After several failures in the same place, I finally caught the action visually. The PVA (left) extruder lays down a raft and several layers, and then exits. Then the PETG (right) extruder comes out, lays down several layers, and exits. When the PVA extruder comes out again, the extruder tip bumps over the draft shield layers laid down by the PETG extruder, causing the spring-loaded build plate on the FFCP2 to noticeably move down and then back up again (can't see it on the video, but I could with my eyeballs). The PVA extruder then lays down another layer of PVA and exits with no noticeable bump, but DOESN'T lay down any draft shield lines at all. Then when the PETG extruder comes back out, it 'air prints' its layer of draft shield, and from there on the draft shield is toast.
Here's a photo of the first PETG layer after the PVA extruder collision
I attached a ZIP file containing the project (.3mf) file, above photo and a short video showing the last PVA and the first PETG layer at the point of failure. This is a very repeatable failure, and I have no clue how to address it. Any ideas would be appreciated.