Impact of Nearby GSM Repeater on LTE Coverage: Exploring RSSI, RSRQ, and SINR Parameters

Hello,
Please help me identify the problem with GSM / LTE coverage. Namely, setting the external antenna to the router, a certain fact caught my attention. Signal parameters generally good - not very good but, RSSI on average about -80, I am able to go down to average about -65, -68, RSRQ on average about -9, I am also able to go down with the antenna set to a constant average of about -5 . However, the problem is with SINR max approx. 8 but very often the average stands at a negative value of -5 and further. The question is where do these disturbances in the signal come from. I noticed one detail on the roof of the neighboring building, it seems to me that it is a GSM signal amplifier antenna which would explain the problems with the signal quality. I attach a photo of the roof with a suspicious antenna - the quality after enlargement is not very good but the antenna element is visible. Please advise people who are in the subject of whether this element on the building can actually be the antenna from the GSM repeater.
Thank you in advance for your help.

PitbullPel wrote:

Please advise people who are in the subject of whether this element on the building can actually be the antenna from the GSM repeater.

Maybe, but not necessarily, it looks more like an external modem of Cyfrowy Polsat to me.

And there is no satellite dish on the building ... Only old type

Do you think everyone must have a package with the Net TV?

Of course, it doesn't ... What the external antenna for Cyfrowy Polsat internet looks like, I know, and the one referred to as neither plus nor CP does not have a fact - someone will write that maybe age and "faded". Apart from the fact of this antenna, if not so, what else can affect such a poor quality of a fairly strong signal ?? Immediately there will be a response - various elements such as obstacles, terrain, etc. My external antenna for the LTE Router is mounted at such a height that it is practically visible from this place the mast is directed, so there are no obstacles. And probably the roof tiles of the neighbors introduce such interference in the signal ...

Added after 2 [minutes]:

The logo on this antenna resembles SignaFlex more than CP or Plus ...

PitbullPel wrote:

What does the external antenna for Cyfrowy Polsat internet look like, I know Plus, and the one referred to as neither plus nor CP has

I have completely different feelings, on the photo that the author gave almost nothing to see, but isn't it similar to this?

Shape like the most ... So look for reasons elsewhere. I understand and thank you for the suggestion. I will also ask my operator to clarify the issue of poor signal quality and such a level of interference, the more that I have a business contract with him for several numbers. We'll see what comes up.