Why wifi long disconnect and then re-connect will appear problems?

[BearPeak]

My project idf is RTOS-v2.0-rc1,and hardware is ESP-WROOM-32.
In my project,the chip wifi is set STA mode to connect phone's hot spots.
When the wifi is connect the phone's hot spots,and transfer sendto() to send data,it is normal work.
But when i turn off phone's hot spots,and wait a few minutes.The problem appeared when open phone's hot spots to reconnect it.It can't normal work just print "wifi: pm start 1 ...".The probability of such a problem is less,but for a product is not allow.Have you everybody encountered this problem?
The wifi code is refer to the official example,Is it due to the cause of the sendto() function?