I may be confused but unless you have gcode defined in OctoPrint's
GCODE Scripts Before and After print job, OctoPrint should just be sending the gcode from the file being printed without modification.
It sounds to me like there may be some absolute (G90) / relative (G91) issues. G28 should set the printers coordinate base, the Z-offset should be defined in the "firmware" (i.e. the EEPROM). If it isn't stored in the EEPROM, then the appropriate M851 command should be inserted where needed.
I have the exact same issue, just did a fresh install of octoprint, have not changed much, ender3 v2, prints perfectly off the SD card, but if i try to print via the web interface the nozzle prints really high as if ignoring my Z offset of -1.35. also there is no display of an ongoing print on my printers LCD display, it stays on the default home page like when the printer is idle. I am using BL touch.
The Ender 5 Plus (and I think the CR10-S and CR-X) have a screen that stores Z-offset code in a menu that can only be reached during a print. Could this have anything to do with it? The Z offset being set on the printer affects the Z offset value, but maybe OctoPrint doesn't invoke it.
Same problem here - printer CR6SE. Printing from SD works great, but Octoprint sometimes ignores the Z-offset and starts the print with the nozzle to low. But not always, which bugs me to no end. And usually just stopping the print and starting it again helps.
Just to clarify some wording here. It isn't OctoPrint that ignores anything here. OctoPrint will send to your printer whatever is in your GCODE file and it's the job of the printer to interpret that correctly. If the printer's firmware requires some non standard print start routines in order to properly work and position stuff, that's a) a bad idea on the firmware's part and b) needs to then be taken care of either in your slicer or the print start GCODE configurable in OctoPrint.
Why does the same print work from SD and not via serial connection? Probably because the firmware knows what needs to be done before a print and does it for SD prints, but doesn't do it for commands received via serial. Long story short: this is a firmware issue, not "OctoPrint ignoring something". Please stop claiming the fault is with OctoPrint here when your printer doesn't adhere to established communication standards.
I´m really frustrated in Octo at the moment für the "Z-Offset"-issue. Just copies of an print wouldn´t work and if i want to make series of an model, it scratches the plate or prints in the air.
I even leveled all the time and made measuring, probing with my CR-10 (Ender 5 Plus) and it ruined two of my PEI-Plates. At the moment, i hate 3D-Printing for that.
I don´´t know what happened, about 100 models haven´t any issue. I checked and changed the bltouch, started probing 100 times. From SD-Card everything works fine. But i don´t want to walk in the basement everytime i modeled something.
