CRH is applied only when the neighbour cell belongs to a different LAC. By applying this value only in cells which are at the border, then the only “different LAC” seen is the one from your neighbour country. In other words : it doesn’t impact your network, but only prevent your MS from roaming too soon.
def CRH = 6dB, so you should raise yours.
Note: CRH works only towards neighbours which are declared in the OMCR. Are your neighbour country’s cells declared as neighbours ?
If yes, then I guess they are also declared for Handover ?
In this case, increase the HO MARGIN.
If no, then there is still a chance that the neighbour cell is using the same BCCH as one of your own neighbours – in such case the MS will not make the difference. It can go and camp on the “other country” cell, because its BCCH was seen as being one of the possible neighbour.
In that case, CRH will work ! (because the MS is able to read the LAC of the neighbour when doing the C2 calculation)
don’t forget that CRH works only with C2 criteria. Ensure your C2 is enabled.