OctoPrint/OctoPrint 1.2.10 on GitHub

Improved performance of console output during plugin installation/deinstallation
Slight performance improvements in the communication layer
Log small log excerpt to octoprint.log upon encountering a communication error.
Changed wording in "firmware error" notifications to better reflect that there was an error while communicating with the printer, since the error condition can also be triggered by serial errors while trying to establish a connection to the printer or when already connected.
Support downloading ".mp4" timelapse files. You'll need a custom wrapper script for timelapse rendering for this to be relevant to you. See also #1255
The communication layer will now wait up to 10s after clicking disconnect in order to send any left-over lines from its buffers.
Moved less commonly used configuration options in Serial settings into "Advanced options" roll-out.

#1224 - Fixed an issue introduced by the fix for #1196 that had the "Upload to SD" button stop working correctly.
#1226 - Fixed an issue causing an error on disconnect after or cancelling of an SD print, caused by the unsuccessful attempt to record print recovery data for the file on the printer's SD card.
#1268 - Only add bed temperature line to temperature management specific start gcode in CuraEngine invocation if a bed temperature is actually set in the slicing profile.
#1271 - If a communication timeout occurs during an active resend request, OctoPrint will now not send an M105 with an increased line number anymore but repeat the last resent command instead.
#1272 - Don't add an extra ok for M28 response.
#1273 - Add an extra ok for M29 response, but only if configured such in "Settings" > "Serial" > "Advanced options" > "Generate additional ok for M29"
#1274 - Trigger M20 only once after finishing uploading to SD
#1275 - Prevent M105 "cascade" due to communication timeouts
Fixed wrong tracking of extruder heating up for M109 Tn commands in multi-extruder setups.
Fixed start of SD file uploads not sending an M110.
Fixed job data not being reset when disconnecting while printing.

OctoPrint/OctoPrint 1.2.10 1.2.10 (stable) on GitHub