5dB is acceptable, no problem !
it is above 8 or 10dB that you should start worrying.
KPI impact : smaller coverage, CSSR and CDR are a little bad (especially at the cell border, when coverage starts to decrease). High amount of HO due to bad level (UL or DL, depending on the direction of the imbalance)
And if the link imbalance is only on one TRX, you’ll see a poor TCH allocation success rate on this specific TRX, while all other TRX are good.