Same problem here, but very intermittent.  I think it is a problem with
the timer that controls this test of the light somewhere in the
instrument panel.  I have not bothered to fix it, it usually stops
flashing if I restart the car.  Too many other more pressing things to
fix, or trips to go on!
--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia
'65 MGB (Driven since 1969)
'74 MGB GT (Restoring)

Assisting on Restoration:
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Parts cars:
'68 & '73 MGB, '67 MGB GT