Z750 Starting issue

[Neio79]

So,  I appear to have a very strange fault on the zed which is causing my garage and me some head scratching so I am throwing it out to the forum for any suggestions.

So Long story short. had some work done on the bike ( rear shock, brake lines, bar end mirrors) upon picking it up it failed to start. with FI flashing up on dash.
checked it out no obvious fault. Changed battery, checked fuses etc no change.
Get the diagnostics done, code showing crank positioning sensor faulty.
Change that, garage report bike starts and runs ok, great, go to collect it. won't start. again check fuses, battery, side stand switch, tilt switch, all good yet won't start.
Bump start it fine and it runs.
Take it for a blast and while riding its giving a strange issue, as soon as the revs drop below 4.5K in any gear including neutral the FI symbol flashed with the red light.
As soon as you get above 4.5K the FI clears.
The bike was riding, idling, accelerating with no issue at all, no flat spots, no mis fire, no stutter. nothing.
Get home, hit the kill switch and immediately try to fire her back up and nothing , tries to fire but won't.

This is baffling,  and the garage are having it back in next week for more checks, however I though I would throw it out here for the combined knowledge and possible solutions. The garage think it might be an earthing to ground issue?

AS right now i am close to committing insurance fraud to get rid of the thing.  Also I want it working for the road track day I have just booked.

[PJ]

I can't really offer any good advice or input, except to say on my ZX6R G1 many years ago I had a bad earth wire which manifested itself by failing to start when hot but bump starting it worked. From cold it started fine though.

[Alzo]

The battery change...was it a new battery or just another battery...I had similar symptoms with a Honda a few bikes back...battery had beef to turn starter motor...but not enough spare to power up ignition system.

[Neio79]

Turns out it was a corroded connector , all sorted . in time to sell lol

[Alzo]

Good stuff...get a Panigale 1299.

[Neio79]

Good stuff...get a Panigale 1299.

Ill stick with the 848 for now