SD position and pause print (UPS, recovery after power loss + octoprint)

Hello,

I am currently developing a plugin for octoprint, to add the management of an UPS and I set up a system of recovery after power loss.
for that I put the print in pause and I recover the position in the file.
In USB the position is good (octoprint) but when printing SD, the number of byte recovered does not correspond to the position where it stopped the print.
most often the position corresponds to the last two lines to play.
I do not understand why, the pause time is more than enough for the printer to give the right position.
I miss maybe a configuration?
my recovery system, works well.
I can resume a print, it just misses me the right position for the SD

need help

Marlin 1.1.9

Edited 1 time(s). Last edit at 06/20/2019 07:38PM by devildant.

I found by myself, the command M27 answer No sd printing in case of pause, suddenly with the buffer I do not have the last value of status.
I modified the source code of marlin to add an option to this command M27 to force the sending of a new message even if the print is pause / stop (I create a new message to avoid interfering with the treatment "octoprint" which is based on the return of M27 to indicate whether or not the printer prints in SD)


I will have to do a tutorial "modify marlin" with my plugin