Why can not get the value from the chunked response body?

Here is the related code:

web_reg_save_param(
                    "ParamName=responsePG",
                       "LB=",
                       "RB=",
                       "Search=Body",
                       LAST);
     
    web_url("event-stream",
        
        "Url=http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t={eTime1}&lastEventId=&r={eventr1}",
        LAST);

Here is the response of the request:

vuser_init.c(181): web_url("event-stream") started [MsgId: MMSG-26355]
vuser_init.c(181): Notify: Parameter Substitution: parameter "eTime1" = "1465581374407"
vuser_init.c(181): Notify: Parameter Substitution: parameter "eventr1" = "6226330001163687"
vuser_init.c(181): t=33935ms: Already connected [0] to perftoolss:80 [MsgId: MMSG-26000]
vuser_init.c(181): t=33935ms: 649-byte request headers for "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113)
vuser_init.c(181): GET /meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=62263300011
vuser_init.c(181): 63687 HTTP/1.1\r\n
vuser_init.c(181): Referer: http://perftoolss/meiwi/app/login/login.html\r\n
vuser_init.c(181): DNT: 1\r\n
vuser_init.c(181): UA-CPU: AMD64\r\n
vuser_init.c(181): X-XSRF-TOKEN: AWBQyZTyzyv9kBfalyFnAxAB0;AWBQyZTyzyv9kBfalyFnAxAAAAAA0\r\n
vuser_init.c(181): User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Win64; x64; Trident/7.0; .N
vuser_init.c(181): ET CLR 2.0.50727; SLCC2; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)\r\n
vuser_init.c(181): Accept-Encoding: gzip, deflate\r\n
vuser_init.c(181): Accept-Language: en-US\r\n
vuser_init.c(181): Accept: */*\r\n
vuser_init.c(181): Connection: Keep-Alive\r\n
vuser_init.c(181): Host: perftoolss\r\n
vuser_init.c(181): Cookie: cvwUN=admin; ss-id=sQrjjUU1t7LGryq77n49; ss-pid=YCBMDwWfFxiHGTdnrnEV; autoLogoutTi
vuser_init.c(181): meout=1200000\r\n
vuser_init.c(181): \r\n
vuser_init.c(181): t=33943ms: 296-byte response headers for "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113)
vuser_init.c(181): HTTP/1.1 200 OK\r\n
vuser_init.c(181): Cache-Control: no-cache\r\n
vuser_init.c(181): Transfer-Encoding: chunked\r\n
vuser_init.c(181): Content-Type: text/event-stream\r\n
vuser_init.c(181): Vary: Accept\r\n
vuser_init.c(181): Access-Control-Allow-Origin: *\r\n
vuser_init.c(181): Access-Control-Allow-Methods: GET\r\n
vuser_init.c(181): Access-Control-Allow-Headers: Content-Type\r\n
vuser_init.c(181): X-Frame-Options: SAMEORIGIN\r\n
vuser_init.c(181): Date: Fri, 10 Jun 2016 17:56:26 GMT\r\n
vuser_init.c(181): \r\n
vuser_init.c(181): t=33947ms: 5-byte chunked response overhead for "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113)
vuser_init.c(181): 223\r\n
vuser_init.c(181): t=33947ms: 2-byte chunked response overhead for "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113)
vuser_init.c(181): \r\n
vuser_init.c(181): t=33948ms: 547-byte chunked response body for "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113)
vuser_init.c(181): id: 1\n
vuser_init.c(181): data: cmd.onConnect {"userId":"2","displayName":"ElisaZ","channels":"autoupdate","profileU
vuser_init.c(181): rl":"https://raw.githubusercontent.com/ServiceStack/Assets/master/img/apps/no-profile64.pn
vuser_init.c(181): g","id":"Do2krnfpfaiOuSi0BD5C","unRegisterUrl":"http://perftoolss:80/meiwi/api/event-unreg
vuser_init.c(181): ister?id=Do2krnfpfaiOuSi0BD5C","heartbeatUrl":"http://perftoolss:80/meiwi/api/event-heartb
vuser_init.c(181): eat?id=Do2krnfpfaiOuSi0BD5C","updateSubscriberUrl":"http://perftoolss/meiwi.services/event
vuser_init.c(181): -subscribers/Do2krnfpfaiOuSi0BD5C","heartbeatIntervalMs":"10000","idleTimeoutMs":"30000"}\n
vuser_init.c(181): \n
vuser_init.c(181): t=120651ms: Inactive socket [1] was closed by www.bing.com:80, probably due to Keep-Alive timeout [MsgId: MMSG-26000]
vuser_init.c(181): t=120651ms: Closed connection [1] to www.bing.com:80 after completing 1 request [MsgId: MMSG-26000]
vuser_init.c(181): Error -27780: Timeout (120 seconds) exceeded while waiting to receive data for URL "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" [MsgId: MERR-27780]
vuser_init.c(181): Aborting download of URL "http://perftoolss/meiwi/api/event-stream?channels=autoupdate&t=1465581374407&lastEventId=&r=6226330001163687" (RelFrameId=1, Internal ID=113) (e.g., due to the target document or object being deleted) [MsgId: MMSG-26507]
vuser_init.c(181): Error -26377: No match found for the requested parameter "ParamName=responsePG". Check whether the requested boundaries exist in the response data. Also, if the data you want to save exceeds 28000 bytes, use web_set_max_html_param_len to increase the parameter size [MsgId: MERR-26377]