Hi RK,
Tuning will depend on what config do u wanna have: more or less traffic in 1800 band?
The reason u’ve got no drops when drive testing is probably that ur call has been holding by the less “interfere” band probably the 1800? And problem can occur only cell got loaded.
So u must check first the call drops statistics per band; it exists within E/// and then do drive test by takin special look at that band.