After reading about 2.4ghz vs 5.8ghz, i decided to give it a go.So i changed to 2.4ghz, first of all i lost wifi (android), solved that issue with otg-cable.
I get connected, ready to fly, all is good. Except a couple of things.

I can't enable anything in the "visual navigation settings", obstacle avoidance etc...
Can't enable rth at current altitude.
Can't adjust low battery warning.
No signal under the image transmission setting.
Can't enable gesture controll.

All of this occurred when i changed to 2.4ghz and otg-cable.

Any ideas why??

probably because OTG is not supported for Spark.
but i'll let DJI and the other forum members weigh in..

Solved..
Installed dji go 4 v. 4.1.15.
Works fine with 2.4ghz and otg now

thanks for letting us know!

Kimjorgen Posted at 2018-2-27 12:52
Solved..
Installed dji go 4 v. 4.1.15.
Works fine with 2.4ghz and otg now

Yes, for the time being this is the only solution to have OTG working on Android.

I had almost same experience but using IOS

Now back using 5.8Ghz

Can I throw something out there? If you all would search the forum first you would save yourself the time of posting a redundant thread that had been beat more then my X wife (joke) OTG doesn't work with Android unless using DJI GO 4.1.15 or lower. Mods please sticky that!

I haven't used the OTG cable with the Spark, but I have a Mavic Pro that uses the built-in OTG cable to side of the Remote. Honestly, the connection on Ocusync disconnected once I got far in range, further than I usually get with the Spark at similar spots, and the connection was spotty and so I don't think going from WiFi to OTG really will improve the transmission if the Ocusync from Remote to Phone can't handle the range distance itself?