Tried all that, it still fails under high load.

>If your Server and Client OS are at the latest Updates, you can use SMB2 and SMB3 without Problems with DBF Files, if you configure the SMB Parameters:
>

>Windows Registry Editor Version 5.00
>
>[HKEY_LOCAL_MACHINE\system\CurrentControlSet\Services\LanmanWorkstation\Parameters] 
>"DirectoryCacheLifetime"=dword:00000000
>"FileNotFoundCacheLifetime"=dword:00000000
>"FileInfoCacheLifetime"=dword:00000000
>

>
>We have added these REG Keys to our Setup, so we can be safe with SMB2.
>We use this since 2012 an we have no Problems at several Installations / Cusomers.
>
>HTH