Please use English only on this forum and please use proper tags for your posts (you refer to an openSPOT2 but tagged the post as openSPOT4).
You should run DMR AutoCal as Tyrbiter mentioned, or manually adjust the RX offset on the Modem page in +-100Hz steps from -500Hz to +500Hz for the lowest BER. You can verify settings using the openSPOT2's built-in local echo service on DMR ID 9999.