jquery - Prevent client from not sending complete data to REST api - NGINX 499 - Cordova -

i have enterprise application built using cordova uses jquery request rest api on nginx server.

i have around 3000 devices running application without issue.

my api requests send key/value pairs , followed larger string of base64 encoded data assigned key in same request.

url looks this:

https://myurl.com/api/?some=keys&another=key&base64=<real long base64 encoded string>

there small subset of devices managed separately others having issue sending complete data request , seem close connection causing server receive of key/value pairs in request , not complete base64 string.

the nginx server shows these requests 499 response.

are there headers or can try use prevent client closing connection? or way resolve issue without breaking multiple requests?

thank you.