Is your drop reason SS on UL, DL or BL?
If your frequency plan is OK (as well as Frequency Hopping parameters – if used)then probably the bad quality can be due to low Signal Strength which may be a result of coverage issues.
Hardware problems may be a cause to the bad quality drops experienced.
The solution to such problems may likely involve antenna physical parameters reviews including re-orientations, height reviews as well as tilt changes (depending on site location-urban/rural).
For the case of low UL SS drops you may need to boost your UL SS with a TMA.