E410/E600 Downgrade

In several AP i have the latest firmware 4.2.1-r12 and i found that a specific model of PDA in not able to optain the IP from our DHCP. This problem not happen with fw 3.10.3-r3, if i try to flash the old firmware form CNMAESTO return : “SW update file download failed”, i have also try to load the fw from ap webpage but same thing.
In same APs i have solved switching to backup firmware but other Ap have a different backup firmware.
It is possible to do a downgrade of the fw?

Hi Steven,
You can download the image to any version but can you please let me know what it is not working in your setup.

For downloading image from 4.2.1-r12 to 3.10.3-r3.
1st downgrade the APs to from 4.2.1-r12 and then downgrade to 3.10.3-r3.

Hi Ashok, with the fw 4.2.1-r12 the PDAs used on our warehouse are not able to Obtain IP from our DHCP. I will try to install fw