There is no link in the documents section to the service manual. I know this having put the link there myself, to Tascam's site for all the DM24 pdf's. I expect you are missing the nuance of a service manual originally written in Japanese translated into English. You are after all, French.
However Tascam's page on the DM24 does contains these two documents regarding software updates and initializing the DM24 to factory settings. Both of which describe the same reset / initialization procedure you protest so loudly, that you fear will destroy a user's DM24.
"UPDATING THE DM-24 FIRMWARE VIA MIDI"
http://tascam.com/content/downloads/pro ... _16_02.pdf
"DM24 DOWNLOADS UPDATE INSTRUCTIONS" "dm24_v3update_iffwdm_only"
http://tascam.com/content/downloads/pro ... m_only.pdf
They both conclude that after installing new firmware via MIDI, that -
"....you will need to initialize your DM-24....
INITIALIZATION PROCESS
1. With the power OFF hold down the 2nd F button (far left of the board), the HIGH button (just above in the EQ section) and the – button (just to the right in the LIBRARY section) while you turn the power ON.
2. The DM-24 will boot to DIAGNOSTIC MODE. As soon as you see DIAGNOSTIC MODE on the display you may release the 2nd F, HIGH and – buttons.
3. Use the “Down cursor key” to move the indicator to SRAM INIT (NOT SRAM INIT for factory TEST) and press ENTER.
4. Press ENTER again to confirm when prompted. A check mark will appear in the box next to SRAM INIT on the display.
5. Use the “Down cursor key” to move the indicator to FLASH INFORMATION CLEAR and press ENTER.
6. Press ENTER again to confirm when prompted. A check mark will appear in the box next to FLASH INFORMATION CLEAR on the display.
7. Use the “Down cursor key” to move the indicator to EXIT and press ENTER. This will reset the DM-24 back to the original factory settings and the DM-24 will reboot. "