BC66 AT+QISENDEX wrong response

I use BC66-NA.
After using a command AT+QISENDEX=… must appear response SEND OK. But from time to time this answer is not correct. From time to time it appears with one missing char, for example SEN OK, SND OK, SED OK. If you say that problem is in uart connection, I’ll ask, why a problem of missing char appears only in this place?
How to solve this problem? Checking for multiple version of answers?

Are commands or programs executed by MCU?I think it’s possible that the data stack you defined overflows,You can weld the module’s main serial ports (TxD, RxD) ,then execute the AT Commands manually,try it again!

I can’t understand why you decided that data overflows? Data sended by MCU can vary by size and this problem comes on different packet sizes. MCU is receiving data from BC66 by command AT+QIRD in size up to 300 bytes w/o any problems, data corruption, etc! Any another commands are executed w/o any corrupted answers or any similar behavior. Only in this place only by this command I’m getting from time to time wrong answer. I have checked all possible inconvenience in connection between MCU and BC66 before writing this post.

I recommend disconnecting the MCU from the BC66 and debugging the module through the URAT port alone

Fixed by migration from IRQ to DMA.