2006 Citi Rhythm electronics cutting out

[JJL1]

Hey all, first post here

I have a 2006 Citi Rhythm, and it has an interesting problem, almost every time I want to start it, the car will swing but never actually start, all the lights come on, except the battery light, in order to start it, i need to disconnect the battery, reconnect it and then start it, then the battery light will come on. (Depending on the temperature of the day/car, I have to be quick or I will have to do it again)

Then while driving, after random amount of time, all the gauges except the speedometer will drop, the oil light will start flashing and an alarm beep will sound 3 times, but the engine will continue running.

List of things we have replaced/tested:
Battery replaced
Alternator voltage regulator replaced
Main engine fuses replaced ( both the housing and fuses, replaced with in-line fuses, not my choice but that's an auto electrician for you)
Positive, negative & earth cables from battery replaced/terminals and connection points cleaned
Tested a different Shurlok box (single plug), same problem except the engine cuts out right after starting (99% sure that this box is faulty)
Cleaned all the contacts on the other boxes with electrical contact cleaner spray

This problem started in winter 2 years ago when it would rain, took the car to an auto electrician, who after having not answer, sent it to someone else who "fixed" the body control module. This caused the problem to go away until summer, now it happens when it is hot.

I am now thoroughly stumped.