Erratic Voltage

[SkyMac]

Hi Everyone

Looking for some guidance, I am experiencing the following situation.......

1. Overvoltage tripped, front alternator light came on just a second before overvoltage.

2. Reset during flight following procedure, issue returned immediately.

The following checks and rectifications have been carried out.

1. Voltage front alternator, erratic at 29.2 to 30.5 through to 2100RPM, even at idle it remains erratic at 29.2 to 30.5.

2. Voltage rear alternator is stable at 27.7 through to 2100RPM and at idle.

3. Regulators checked, front and rear deemed functional.
(Decided to replace with zeftronics anyway).

4. Over voltage sensor checked and deemed functioning correctly
(Decided to replace with new from Cessna, 49 years old, time for new)

5. Front alternator checked and found to have a slipping drive as well as internal bearing issues. Only 260hrs since O/H, replaced with complete off-shelf O/H assembly and new drive.

6. Diodes checked and found to be functioning correctly.

Why I need some guidance.....

The front alternator continues to deliver erratic voltage to the buss bar at 29.2 to 30.5 (and occasionally higher), it is as if the voltage regulator is not being told to regulate the voltage, and we are getting raw voltage from the alternator to the buss bar. I have checked all wiring and did find a bad connection at the regulator connector, fixed but no change.
When I switch to the rear alternator it controls fine at 27.7v with almost no change. So we did a quick change of regulators by swapping the front for the rear as quick test.
Even after the swap the previously front regulator now on the rear, it was working fine at 27.7 and the rear now connected to the front was erratic at 29.2 to 30.5, keep in mind these are both new zeftronics

So the issue seems to be with the front system, any thoughts?

As a footnote, during the resto every switch in the panel was replaced with new from Cessna including every terminal connector, and we have re-checked the connections.