I had the same issue recently and I researched on this topic.
I could not update it from the joomla direct 3.9.1 to 3.9.2 not even by uploading it manually.
A reason was that before this update it forced me to upgrade the php version to 7.2 so I did it from a cpanel, now to solve this next update will be as follows :
1. Login to the cpanel
2. Find " MultiPHP INI Editor" under the software
3. Choose the domain and select the edit
4. Set :
"max_execution_time " to 90 (it was in mine only 30)
"memory_limit" to 256M (it was by the new php enabling 32M only !)
"post_max_size" to 100M
"upload_max_filesize" to 100M
As every php new version is set to the default.