Found this in the respository, as in Octoprint my temps always go away while printing. (and this fix definitely fixed the display tempeature in Octoprint. But..
Just a heads up, not sure if it is for sure related to this plug-in for sure or not, but I had JUST installed this and never seen this before. 3 or 4 print attempts in a row with the cgode (I opened in in textpad) set for the hotend temperature of 205, Octoprint kept trying to set my temperature to 260.
Hi @derekpurdy!
That plugin doesn't have anything to do with the sending of gcode, only receiving it and fixing it.
The issue you have is likely something else - might want to try printing using safe mode to make sure it is not a plugin issue.
Please upload one of those gcode files for the devs
Thanks for the reponse just finished reassembling my hotend to make sure nothing was melted or damged as that seemed pretty hot. I disabled the plug-in for now, and loaded just the standard xyz cube and it loaded fine. I want to try again after this calibration print is done with the plug-in enabled and disabled.
Nothing in that gcode to suggest the temp should be set to 260.
Can you enable serial.log (<- click link to find out more), print that gcode then once the issue is reproduced, upload the logs. Thanks!
Enables us to see if OctoPrint is sending those commands to the printer, or something is wrong firmware side.
If you, as Charlie suggests, upload the logs, the plugin will output what messed up temperature it reads, and then what it parses it to, and sends to OctoPrint. If the error lies with the plugin, the logs will tell.
I have personally tested the plugin on 3 different Ender-3 v2's, and all seemed to report the right temperatures.
@AlbertMN Seems from your plugin source that would only be reported at debug level, which most users don't have - so that might not be useful in this case. And it seems unlikely to me that your plugin is to blame for this. But we shall see...
Temperature seems to be being set to 410....! This line:
2020-09-08 15:44:32,001 - Send: N5 M104 S410.000000*75
is the offender.
Can you upload an octoprint.log too - fastest way for me to see what plugins etc. you have, that might be the issue.
A quick test with the Ender-3-v2-Temperature-Fix plugin disabled STILL did it with this specific gcode. which was generated using the same CURA as all my other prints. So it doesn't appear to be plugin related. (At least this plug-in)
Sorry for pointing fingers so quickly, just NOTHING else had changed other than this gcode file and the plugin.
I will grab the octoprint log.
Different plugin, definitely then. Comparing the gcode, it goes from M104 S205 in the file you supplied, to M104 S410.000000 in the serial.log. Only thing in the way is a plugin.... but which... 
@Charlie_Powell right, good point 
@derekpurdy Well, glad to hear that this isn't a problem with the plugin, as it's been pushed to quite many users already. You seem to be in good hands though ^
ehh now I'm stuck... No recommendations other than to try safe mode, since I can't see one that seems likely it might be causing the issues.
Then.... If you don't mind, (its quite a long process) you need to eliminate the plugin that's causing the issue! Fun right.
I recommend going for half, then testing, then half again if the problem persists. Cuts through them quite quickly
I'll give safe mode a go first.
safe mode, no issue set it properly to 205.
I'll see if I can get some time later tonight to go through all the plugins.
Yeah, I appreciate its a long process. I had to do it for an issue I had before, and did take a while. But, you can live with the fact you may help someone else who has the problem. At least we know we're barking up the right tree.
I'll catch up with this topic tomorrow, for me. 
My money is on Filament Manager. That one at least rings a bell with regards to unexpected temperatures being set.
yeah, the fact it's setting it to 410, which in F is actually 210... a coversion is definitely wrong or failing.