RDR-4B
Last night, somewhere in Yangon FIR, our lovely RDR-4B showed a 20NM red cell at FL390, no high terrain anywhere in sight, full ground contact (tried ELEV, ON PATH, gain, still wouldn't go away) ... when we got closer (30 NM) the "cell" vanished without a trace.
Later on, between Chittagong and Kolkata, intense lightning ahead, our lovely radar was asleep, nothing on the display (tried max gain, elevation down up to FL290 still no returns) ... we started avoiding the beast by following traffic below and looking out for flashes ... when ~40NM from the beast, out of nowhere, a large (30-40NM) red/magenta circle appeared.
Can't trust this radar after that, no way to plan ahead ...
We were lucky to be on a populated track out of clouds at FL390, the radar was useless