I seem to have problems to get Gigabit connections running.

I am referring several routerboards that with gigabit interfaces (rb1000, rb1100AG, CCR, some SXT's with G-interfaces)

Usually I crimp the cables myself, shielded, with shielded connectors. (I tend to buy the best the market can sell me because I am fed up with so many failures, to no avail though..)

Short cables, even non shielded pre-fab cables usually are no problem. Connect and get Giga connection.
Even my own crimped non-shielded short cables get Giga links running (!) But they have to be short.

But make the cables a couple of meters long, or put any make or type (all Gigabit type) power shot in between two Gigabit routers and I get only sometimes a gigabit connection. Or it runs for months and then never to be able to get them back again as gigabit. Even not when forced. 100Mb is fine though.....

Usually I refer to cables that also has to do PoE. On most Gigabit units nowadays its even not to be avoided to use same network cable for poe and data connection.

I have seen the issue on well earthed units, as well as on non (plastic!) units.
I have seen the issue on both of the wire schemes for utp/ftp (wg-g-og-b-wb-o-wb-b or wo-o-w-b-wb-g-wb-b) (Off course not mixed. Both end of the cable should be the same. I even made sure the whole chain of cable-powershot is the same)

The moment I connect 3rd party (TP-link, ubnt) I never seem to have same issues... WHY?

Is MT used Ethernet chip still very sensible for errors? I mean, I have had the port flapping issue for years and some routers still do that.
Sometimes all it takes is a powercycle to bring the gigabit back. But sometimes it never comes back, sometimes only for a limited period of time.

In the 'old' days it wasn't very important. But now I have to run several 100Mb+ backhaul links and now I can only do that by bonding interfaces or running two links side by side (gives me more redundancy though....).
All this is also the reason I would really welcome more ports than only on on almost every unit/board leaving MT factory....

Anybody else having same issues? Or solutions? It's driving me crazy.

what type of gigabiut poe injectors are you using? Can you post pics - some of the originals are bad / faulty I have found.