I think you are looking at a ping-pong HO between 900 and 1800, due to “better conditions”.
The bad Quality is not reflected on the HO : 95% of HO are BC !!
Therefore you are probably looking at a parameter issue.
On the other hand, you are saying that the problem appears randomly, as “peaks” during the day. Which would suggest that this is a software problem…
So I don’t know.. based on QoS stats from NPO, can you specify the problem a little better ?
I don’t think Abis or drive test would help here : you should be able to find much more info from NPO indicators.