Spontaneous FunctionTimeoutException

we have several javascript functions (http , servicebus triggers) running in consumption plan function app.

of these functions fail functiontimeoutexception, causes entire app hang 10-15 minutes (servicebus triggers not called, requests http triggers return 503 code). traces in application insights show host.executor logs (function started/completed, etc), without our logs.

these exceptions occur spontaneously in different functions, usual execution time of varies 50 ms 10 seconds. functions work different cosmosdb collections, metrics of these collections show consumed ru , number of requests under limits.

have non-default app settings:

    "http": {          "maxoutstandingrequests": 100,                  "maxconcurrentrequests": 10      }

in host.json preventing eacces errors under large http request rates (perhaps requires further adjustment)

    "servicebus": {          "maxconcurrentcalls": 1      },

in host.json , website_max_dynamic_application_scale_out = 1 in application settings temprorary solution until servicebus session became supported (https://github.com/azure/azure-webjobs-sdk-script/issues/563).

can these errors caused our settings?
idea move http triggers separate app (perhaps classic plan)?

example function:
2017-10-31t15:26:08.782, 7a2a8243-b442-4fbe-aa31-8f3e4442a104, south central us

Microsoft Azure  >  Azure Functions