Message: Failed to unmount '/system'

[dc_01]

Hi there, i have a question with TWRP 3.2.1-0 OREO: I always ge the message "Failed to unmount '/system'", see the screenshot attached, as well as the two logs created by TWRP.
What can i do to solve this issue and what will this issue cause?
Any feedback is much appreciated.

Thx