Invalid refresh token

Hello. I have some issues with tokens refreshing.
After I obtained my tokens, I can do the refreshing only a short period of time.
From various reasons, my access_token cannot be refreshing after a few days (~5 days, althought in SmartThings developer write that refresh token expiration is 30 days, so my refresh token is valid). I received the following response
“{
“error”: “invalid_grant”,
“error_description”: “Invalid refresh token: ce65ad60-f007-4f98-9e66-79e2a78a21ab”
}”
Also, in their documentation
" The authToken expiration is five minutes; your SmartApp is expected to make calls to the SmartThings API within this duration after receiving the request from SmartThings. "
But when I do the refresh tokens WS, I receive other value for access_token “token_expiry” = 86400 sec. Which is the correct value for access_token validity and which the reason of the issue refreshing tokens?