First clean all indicator light bulb connectors in front and back. You may have a bad contact. That also causes no or slow blinking due to poor current flow (if current does not flow from relay, relay timing will not work as far as I know). Happens especially after car has been sitting for a while and oxidation accumulates on contacts. I have had this happen on my MGs over the years and some cleaning and wiggling of bulbs fixes it.

My Mercedes occasionally freezes (once a month) but it seems to be a stalk-hazard switch bad contact issue that is solved by switching either one on and off.

Bert

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'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8