Little update and possible work around.
Opened world with "broken" command block in MCC Toolchest
Edited command block to have correct command
Saved world
Opened world in 1.16.100
Command block worked correctly
Right clicked on block, textboxes looked fine
Closed command block
Command block now is corrupted
Baz
Little update and possible work around.
Opened world with "broken" command block in MCC Toolchest
Edited command block to have correct command
Saved world
Opened world in 1.16.100
Command block worked correctly
Right clicked on block, textboxes looked fine
Closed command block
Command block now is corrupted