Household Surge Protectors - Good or Bad?

A few weeks ago I had a surge protector installed in my breaker panel.

It was a new variey I had not seen before, in that it took the place of two standard sizede breakers and connected to both phases of the breaker panel supply

Since then we’ve had had a couple of power outtages and all the household devices kept running upon power restoraton - so far so good :-)

This past week I had reason to disconnect power and speaker cables to loan to a friend for audition.

Afterwards I reconnected the power cables to the amp and powered up.

NOTE: the system is on a dedicated line - it’s breaker was not touched by the install

Immediately I noticed a hum from the amp, where previously there had been none - even at full volume with the phono stage selected.

After lots of analysis and testing, I remembered the installation of the Surge protector.

I measured the impedance between the ground and the neutral and found around 5 ohms of resistance.

To temporarily get over the hum I have connected the neutral side of the inputs to a common earth tap on the power distribution box - it has worked like a charm - i.e. until I can get the electrician back here to fix the real issue.

So my question:
- Is this just sloppy work? - I’m assuming that the neutral of the dedicated line was disconnected and not reconnected correctly, OR
- do ALL housewide surge protectors such as the one I have had instlaled always present with this problem?

Thanks for any feedback