I have received a serviced Omnitik 5 PoE and it was upgraded to 7.13.3. All 220 units in our network runs on 6.46.8 and it is stable.
Have tried to downgrade by dowloading the npk file for 6.46.8 in files, click the “Downgrade” button in “Packages” and OK’d the reboot and downgrade.
The Omnitik still comes out wit 7.13.3. Factory software version is 6.35.4 so we are not older.
Can this be done using netinstall or is there another way? We would prefer to have all units on the same version and don’t have to upgrade all the others
netinstall is the best way imho
Do the log files indicate an issue why the downgrade is not done ?
Possibly storage issues, Omnitik 5 PoE is 16Mb device and as of 7.13, ROS7 is known to cause a potential problem on such devices (depending on your config and usage: for some it works, for some it doesn’t).
If possible, try to remove wireless package, then reboot.
Then try the downgrade again. And you will have to reconfigure everything related to wifi again.
Netinstall should work anyhow.
Why not 6.49.10 LT ?
Thank you for the quick response. It was a storage issue.
Removed the wireless package and could downgrade. It is now running in our network with the same version as the other units. 
6.46.8 are more then three years old. You should upgrade to a newer version. Why not go to 7.x for all devices. Sooner or later you will not get more devices that do supports 6.x software.
6.49.11 (just some month old) is long term release and should also be a better choice than 6.46.8.
We are working on it