AntonK

An old (2000) Mobotix, a 2 MP Pelco dome, a 12 MP Indigovision bullet and a 4 MP Milesight minidome

Are these cameras installed on a conductive body? Might be interference from nearby solar panels or something

Changing DVRs is the only viable option that you have, tbh. And would be much cheaper than any 3rd party solution.

There are ways http://www1.dahuasecurity.com/download_detail_60.html

I would not recommend powerline networking for anything security-related - multiple failure points and can not be backed up with UPS.

I've done quite a lot of residential installs with Hikvision and Dahua - totally acceptable quality and reliability at rather low price, however lately I begun offering Milesight - their PTZ with motion-triggered led is a great deterrence and sales factor

A lot, and maintenance cost increase over time. More often or not, the cost of replacement of an old system is negated by the cost of one or two years of maintenance.

I was member of this forum many years ago, since the good old days when I was installing $20 320 line OEM domes, supplied directly from PRC with 10% spare parts (surprisingly, very few spares were actually needed and one camera lasted for over a decade and could've worked more if wasn't replaced by an HD device) and fake (lol) Geovision PCI cards. However, when forum engine was replaced or something, I couldn't log in with my old password, and now I couldn't even remember the username so I thought that I could open a new account as well.