if it's a 1977 (N7) Bulova with a japanese (likely Seiko) module then the fault might be caused by a short sometimes caused by an improper battery.
I installed a correct battery but it turned out that they make this battery in two versions - flat negative top and also with a nipple on top.
This nipple raises the battery by a fraction but solves the problem.
I fixed the problem. The negative battery terminal on module had some corrosion where it makes contact with battery. After cleaning with alcohol and Q-tip the display stopped flashing. Thanks for helping.