transaction validation not working (PATCH with validationOnly:true)

I am getting errors from F5 while validating a transaction. here are the request and response pair.

Request for validation only (capture using fiddler)

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PATCH https://172.17.235.162/mgmt/tm/transaction/1562600278455417 HTTP/1.1

Content-Type: application/json

X-F5-Auth-Token: YNVM7Q4UIP5RJUY6MX7B5WPYXY

Host: 172.17.235.162

Content-Length: 21

Expect: 100-continue

{"validateOnly":true}

Response for Big Ip fails (capture using fiddler)

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HTTP/1.1 400 Bad Request

Date: 08 Jul 2019 15:40:30 UTC

Server: com.f5.rest.common.RestRequestSender

X-Frame-Options: SAMEORIGIN

Strict-Transport-Security: max-age=16070400; includeSubDomains

Pragma: no-cache

Cache-Control: no-store, no-cache, must-revalidate

Expires: -1

Content-Length: 120

Content-Type: application/json

Allow: 

Expect: 100-continue

Local-Ip-From-Httpd: 172.17.235.162

X-Forwarded-Server: localhost.localdomain

X-Forwarded-Proto: http

X-Forwarded-Host: 172.17.235.162

X-Content-Type-Options: nosniff

X-XSS-Protection: 1; mode=block

Content-Security-Policy: default-src 'self' 'unsafe-inline' 'unsafe-eval'; img-src 'self' http://127.4.1.1 http://127.4.2.1

Connection: close

{"code":400,"message":"state must be VALIDATING in PUT request to commit the transaction.","errorStack":[],"apiError":2}