Television displaying mosaics

Yes, you have a very good connection speed and more than enough to watch TV and even several at the same time.

In short, your problem is certainly with the powerline connections. As @brupala says, a good cable would solve all that and for less money..

Yes, it’s the connection between the two that’s getting lost... it’s a problem related to the electrical distribution in your house... you need to try different combinations of your outlets...

First of all, each powerline adapter must be plugged into the first wall outlet... if your adapters have a 220 outlet on top, the powerline adapter must be plugged directly into the wall outlet, and the extension should come from the powerline adapter... No power strips on the wall, just outlets with grounding pins, and if an extension is necessary, the powerline adapter must be on the first outlet closest to the cable...

No fridge on the same outlets, avoid all small phone charger adapters or others, they need to be moved to another outlet... Compact fluorescent lamps too

Maybe swap the two powerline adapters, switch them around.

If you live in a standalone house or in an apartment building with 40 people doing the same thing, it can become impossible... these stacked connections alongside the 220 in unshielded conduits are also influenced by the radiation from Wi-Fi and mobile telephony and other “wireless” gadgets

And in your home, is it not possible to run a cable using the network of electrical conduit? … all this is often feasible by passing a needle through the conduit, which serves to pull the new wire back through...

OK,
so your electrical installation is too electromagnetically polluted to use powerline adapters, the only solution is a direct cable, especially with a fiber connection.

Once again, cat5e is more than enough, especially since you shouldn't have 100m.
cat6a is for 10 Gbit/s at 100m.