Certificate issue?

Hi, I’m a newbie to Tyk and we are having trouble getting our gateway to work.
We have set up Tyk gateway to listen to port 8080 over https. In an earlier stage we just ran http and called a backend service with http also and that worked fine. The target backend service runs in a docker container.
I searched the documentation about this error and it says that we should have the latest version of the gateway. We are on 2.9.2, is that good enough? The docs also says that we should check expiry date on the certificate, and that is in august 2020 so it should be ok.

This is the error message we see in the gateway log:

1 error 4f36fd95bb464e825527d20644b906f3 2020-01-20T16:33:37+01:00 http: proxy error: crypto/rsa: verification error – snuten-dev.kreftregisteret.no:440

The error we get back in postman is:
{ “error”: “There was a problem proxying the request.”}

Any ideas?

Adding som info from debug session in Tyk:
[Jan 21 09:27:38] DEBUG Started proxy

[Jan 21 09:27:38] DEBUG Stripping: /api/PromsFormOrder

[Jan 21 09:27:38] DEBUG Upstream Path is:


[Jan 21 09:27:38] DEBUG Outbound Request: https://snuten-dev.kreftregisteret.no:440/api/PromsFormOrder/reply

[Jan 21 09:27:38] ERROR proxy: http: proxy error: crypto/rsa: verification error api_id=147cb662d8f64e2c78cc23e6f10d825b org_id=5df36c282c09bf08b41e2207 server_name=snuten-dev.kreftregisteret.no:440 user_id=-- user_ip= user_name=

[Jan 21 09:27:38] DEBUG Upstream request took (ms): 25.314547

[Jan 21 09:27:38] DEBUG Done proxy

[Jan 21 09:27:38] DEBUG pub-sub: Sending notification{gateway-log {“api_id”:“147cb662daabbd4e2c78cc23e6f10d825b”,“level”:“error”,“msg”:“http: proxy error: crypto/rsa: verification error”,“org_id”:“5df36c282c09bf08b41e2207”,“prefix”:“proxy”,“server_name”:“snuten-dev.kreftregisteret.no:440”,“time”:“2020-01-21T09:27:38+01:00”,“user_id”:“–”,“user_ip”:“”,“user_name”:“”}