In case of SharePoint web part depends heavily in Viewstate to store large data or request, you may face an issue in SharePoint that sometime data is not saved and if you check the SharePoint logs you will find the below error:
Unexpected Unexpected error occurred in method ‘GetObject‘ , usage ‘SPViewStateCache‘ – Exception ‘Microsoft.ApplicationServer.Caching.DataCacheException:
It seems SharePoint try to cache the request using distributed cache service and this service has default limitations (20 seconds).
To fix the above issue, try to increase the RequestTimeout as the below PowerShell script:
$ViewStateCache = Get-SPDistributedCacheClientSetting -ContainerType DistributedViewStateCache
$ViewStateCache.RequestTimeout = 1000
Set-SPDistributedCacheClientSetting -ContainerType DistributedViewStateCache -DistributedCacheClientSettings $ViewStateCache