ATE出错求助

ATE校准6753，经常会出现连接的错误，同一块板子有时能校过，有时也会出错。请大家帮看看，谢谢。
刚开始校准时会出错，也有LWG校完了切换到LTG时出错。
2016/06/04 17:47:48.891 [GPIB] CMW GSM/EDGE CODE Version: 2014/09/22
2016/06/04 17:47:48.891 [GPIB] GSM/EDGE Verified by CMW_GPRF_Gen,V3.0.11&CMW_GPRF_Meas,V3.0.11&CMW_GSM_Meas,V3.0.10
2016/06/04 17:47:48.891 [GPIB] GSM/EDGE Verified by CMW_GPRF_Gen,V3.2.10&CMW_GPRF_Meas,V3.2.10&CMW_GSM_Meas,V3.2.20
2016/06/04 17:47:48.924 [GPIB] CMW WCDMA CODE Version: 2015/01/13
2016/06/04 17:47:48.924 [GPIB] WCDMA Verified by FW CMW_GPRF_Gen,V3.0.11&CMW_GPRF_Meas,V3.0.11&CMW_WCDMA_Meas,V3.0.10
2016/06/04 17:47:48.924 [GPIB] WCDMA Verified by FW CMW_GPRF_Gen,V3.2.10&CMW_GPRF_Meas,V3.2.10&CMW_WCDMA_Meas,V3.2.15
2016/06/04 17:47:48.924 [GPIB] WCDMA ListMode NSFT Verified by FW CMW_BASE,V3.2.51/V3.2.70,CMW_GPRF_Gen,V3.2.40&CMW_GPRF_Meas,V3.2.40&CMW_WCDMA_Meas,V3.2.70
2016/06/04 17:47:48.962 [GPIB] CMW LTE CODE Version: 2014/12/04;
2016/06/04 17:47:48.962 [GPIB] LTE verified by FW CMW_GPRF_Gen,V3.2.10&CMW_GPRF_Meas,V3.2.10&CMW_LTE_Meas,V3.2.50
2016/06/04 17:47:48.962 [GPIB] ----RCT_Common_SwitchPort----
2016/06/04 17:47:48.962 [GPIB] *RST;*OPC?
2016/06/04 17:48:22.519 [GPIB] BFFF0015[完成操作前超时已过期。]
2016/06/04 17:48:22.533 [*Error*] RCT swtich port failed

你是用什么仪器在校准?

CMW500。

换GBIP和仪器和电脑都试下