Your mast upgrade spoiled my connection!

[Rob64]

I got the Three broadband box a couple of weeks ago to evaluate as my possible primary broadband source.

It looked promising, although I am on the edge of the indoor coverage zone, I worked out where the lone mast was and by putting the router on a little shelf high in the loft eve facing the mast I got a rock steady 'good' 5G signal. Speeds were typically 50 to 100mb, off peak even hitting 180mb at times, other times dropping down to 30mb for short periods. I even ordered an 4x4 MIMO external antenna with a view to mount externally on a pole for more height (height is always good in radio)

Then a few days ago 5G disappeared, the service status page said they were doing mast upgrades to be finished on the 16th. I was looking forward to probably even stronger service.
Its come back on and the workmen have gone, but its really poor!!  With the router in the same position I can only get 'fair' signal, I have spent a lot of time tweaking the position around but cannot get it to improve. Sporadically it flips to 'good' with a sub -100db signal but signal quality -12db is poorer and it quickly flips back to the weaker channel -108db with better quality -3db. I can't get past 20 to 35mb and before it was pretty stable but now the speed wobbles like crazy.

I am really gutted, I was gearing up to cancel my cable broadband and switch to the far better value Three 5G, but its now looking like I will be sending the router back, luckily I only took the 1 month at a time deal.
They have done what ever they did to the mast (big tower - 3 guys up it for days) and gone so its not likely its going to improve is it? and my area (small town) is unlikely to get another 5G mast anytime soon.

[Rob64]

I did, its not changed, I am still just within the indoor and outdoor 5G coverage, network status says all is OK.
I am about 0.55 miles as the crow flies from a big tower with a LOT of services on it.
Whatever they replaced, its either putting out less power or its alignment doesn't suit my location as much as the original kit did.
Even though the mast isn't far, it isn't hugely tall and there are a lot of houses in between it and me. I can't decide whether to persevere and carry on with an external antenna, or just send the router back and go with a fixed line. I can't better position the router on internal aerial, its at max indoor height and facing the tower.

5G is certainly height sensitive as you expect with short wavelength signals, from nothing at upstairs height, to some signal in the loft to much better at the highest point in the loft. An external aerial on a 6 foot mast above roof height could give a super strong signal, but it could be investment without satisfactory result.