L900 (priority 6) to L1800 (priority 7) UE moves to higher priority if nrb cell is better than -114dBm (hys 4dB and 1s).
RSRP Target > QRxLevMin(-60) + ThreshXhigh(3). L1800 RSRP is way better than this but still doesn’t re select.
What you have here is L900 to L1800 threshXhigh=6dB with prio7; also L1800 to L900 Threshxlow=10 dB prio6.
It is only 4 dB delta you may have pingpong in reselections.
You may want to increase this delta to 8 dB like this: L900 to L1800 threshXhigh=4dB with prio7; also L1800 to L900 Threshxlow=12 dB prio6.
To reselect to lower priority RSRP should be less than sNonIntraSearch.
Which is not case here, as L1800 RSRP is better.
If RSRP quite good, then no ping pong issue suspected here.
L1800 to L900 snonintra low value and L900 to L1800 snonintra high value to start measurement.
L1800 to L900 thresxlow high value and L900 to L1800 threshxhigh low value.
It will reselect after measurement of minus 116.
Measurements will start at minus 116 to interfreq.
L900.
And reselect better than minus 110.
Discard hyst and offset for a moment.
Threshxlow make high.
For late reselection.
Make 5 to 9 or 10.
But will be aggressive.
As reselection will go less to L900.