arduino pro mini upload crash bootloader

uploading new program on arduino pro mini crash the bootloader.
I'm using 1.8.12.test done with 3 boards ATmega 328p 5V 16MHZ.
need to burn bootloader between uploads.

Does this happen with a specific sketch, or does it happen even when you upload the File > New sketch?

happen first with my own sketch which was working on a pro mini i wanted to reprog with some change.
i was unable to upload the my sketch,try to upload blink example,no upload.Finally burn the bootloader and
success in upload blink but when reloaded blink no upload,need to burn bootloader again.
i'am on win10 with arduino 1.8.12.So i make a test on another pc running win 7,arduino 1.8.2 :same only one upload after burning bootloader.

my sketch work well on a Nano without upload nor bootloader problem.
Solved !!! just add Pro Mini DTR to FTDI 1232 DTR.

I'm glad to hear you found the solution. Thanks for taking the time to post an update.

The reason why you could only upload after burning the bootloader when the DTR pin was not connected is because the DTR pin is used to reset the ATmega328P at the start of the upload. The reset is needed to activate the bootloader so the upload can happen.

The reason why you are able to upload without the DTR connection the first time after burning the bootloader is because when you burn the bootloader you erase the flash memory of the ATmega328P, so there is no program in the application section of the flash and the bootloader runs constantly. Thus, there is no need to reset the chip to start and upload. After that first upload, you now have a program in the application section and so the bootloader only runs for a short time after the chip is reset.