This is mentioned briefly in MC-134603, however, they do not seem to understand what's happening.
To recreate:
get a command block (impulse or chain) on always activate.
place it
put in a simple command like /say hi
change the mode to repeat
observe as it will not say anything until you go to needs redstone and back
Environment
I believe that this not relevant, but-
AMD Ryzen 5 of some sort
MSI GTX 970
Windows 10 latest update
latest java update
Please do not mark unreleased versions as affected.
You don't have access to them yet.