help request: plugins question that cant use grpc-transcode with ext-plugin-post-resp

Description

I need use two plugins: grpc-transcode and ext-plugin-post-resp. There is no problem with these two plugins when used alone, but some problems occur when they are used together. When i use grpc-transcode and ext-plugin-post-resp together, the api response is :

{
    "code": 5,
    "message": "Not Found",
    "details": []
}

and some errors in apisix:

access_by_lua(nginx.conf:292):2: in main chunk xxx
/apisix/apisix/init.lua:730: in function 'http_access_phase'
[C]: in function 'handle_upstream'
coroutine 0:
stack traceback:
[error] 57#57: *872933 lua entry thread aborted: runtime error: /apisix/apisix/init.lua:730: attempt to call ngx.exec after sending out response headers

both plugins do their job correctly, upstream grpc service receive the request and returns right and ext-plugin-post-resp also print out logs after grpc service returns. I don't know how I should troubleshoot the problem next.

Environment

• APISIX version : 3.6.0
• Operating system : Ubuntu 16.04.1 LTS
• OpenResty / Nginx version : nginx/1.20.1
• etcd version, if relevant : 3.5.0