XPDR Auto-squawk for TA and RA
That's three incidents now on record where TCAS RAs conflicted with ATC -- JAL the other one.
While the TCAS electronics seem to be doing the job, it looks to me that the ATC human factor has been left out of the design consideration.
It's natural for ATC to get seriously concerned when targets are about to converge on the scope and it's 50/50 that ATC instructions at this point may aggravate the situation, but they have no confirmation that TCAS has taken over. Also crews responding to an RA don't have the time to discuss the situation.
What TCAS should also do is issue different squawk codes for TA and the various RA commands (increase/decrease/halt climb/descend) so that ATC knows what the a/c are up to.
There will still be an up to 10 second delay between radar sweeps, but at least ATC will be notified reasonably soon that they should not interfere with the TCAS resolution.