Google Cloud Workflows - "ResourceLimitError" when doing HTTP requests in a loop

We are using GCP Workflows to do some API calls for status check every n second via http.post call.

Everything was fine till recently all of our workflows started failing with internal error:

{"message":"ResourceLimitError: Memory usage limit exceeded","tags":["ResourceLimitError"]}

I found out, that when we are using GET with query params, it's failure happens a bit later than the same for POST and body.

Here is the testing workflow:

main:
    steps:
        - init:
            assign: 
                - i: 0
                - body:
                    foo: 'thisismyhorsemyhorseisamazing'
        - doRequest:
            call: http.request
            args:
                url: https://{my-location-and-project-id}.cloudfunctions.net/workflow-test
                method: GET
                query: ${body}
            result: res
        - sleepForOneSecond:
            call: sys.sleep
            args:
                seconds: 1
        - logCounter:
            call: sys.log
            args:
                text: ${"Iteration - " + string(i)}
                severity: INFO
        - increaseCounter:
            assign:
                - i: ${i + 1}
        - checkIfFinished:
            switch:
                - condition: ${i < 500}
                  next: doRequest
            next: returnOutput
        - returnOutput:
            return: ${res.body}

It can do up to 37 requests with GET and 32 with POST and then execution stops with an error. And that numbers don't change.

For reference, Firebase function on POST and GET returns 200 with next JSON:

{
  "bar": "thisismyhorsemyhorseisamazing",
  "fyz": [],
}

Any ideas what goes wrong there? I don't think that 64Kb quota for variables is exceeded there. It shouldn't be calculated as a sum of all assignments, should it?