For this issue, I suggest you do a hardreset for the base,then test again.

do a hard rest for W52, the steps are below:
1. connect the network cable to the base
2. long press the paging key on the base and not stop until step3 is finished
3. connect the power to base , waiting for the three lights on the base light up one by one , during the whole process, please keep pressing the paging key !
4. after the three lights all light up, release the paging key and reconnect the power supply

After that, if this issue still exist,please help me get the below info: many phones do customer have? offten does the issue happen?

3.Please send the level 6 system log, config.bin file and PCAP traces to me.  About how to get these files, please refer to this FAQ:  Note: because this is rondomly case, so please export the log to the server side, about how to do that, please refer to the attached guide.