Just for your info, i am on your side with needed additional Heatsink but just for a better feel...
H3 is specified to 125 Degrees maximum!!!! thats nearly the double of 69...
and i read somewhere (i think cnx) that prime or something doesn't get it higher than 100 Degrees there...
H3 will downclock if it gets too hot... this is the inbuilt safety thing... so get a heatsink but no headackes...

btw. in my case there was running an QTdemo default on the image... which is not needed/useless at all... (no display

)
just getting the soc temp higher... (this should be fixed by FA urgently...)
If your NanoPI NEO Crashes... this may be related that you are using a long an thin microusb cable for power...
if thats the case use +5 GND for power on the Debugport and use fat powercables like AWG20 or AWG22...
i had some crashes, and using this solved any issues... no issues for 2 days now,... intensive usage...