Error taking screencap

[freosc]

The error log contains this messsage
ERROR: Unable to retrieve screen capture, aborting rendering...

OpenJDK Runtime Environment (build 11.0.9.1+1-Ubuntu-0ubuntu1.18.04)
OpenJDK 64-Bit Server VM (build 11.0.9.1+1-Ubuntu-0ubuntu1.18.04, mixed mode, sharing)
ADB:
Version 1:8.1.0+r23-5~18.04
Installed as /usr/lib/android-sdk/platform-tools/adb

AFAIK if I manually take a screen capture I have to get rid of the "\r" characters, like so:
adb shell screencap -p | sed 's/\r$//' > screen.png
(without the sed, the png is not formatted correctly)