.NET Runtime error causing application pool to stop

I'm having this error repeat almost every minute, I think to the point it's hanging my web-server as sometimes it becomes unresponsive but still ping-able.

I'm not exactly sure where to start looking for a fix in reading the 3 log entries below.

Running asp.net 4 for a DNN CMS website (Dotnetnuke) on a new install of windows server 2016 standard. Prior this site was on a 2008R2 machine and this has been happening since the migration.

Application: w3wp.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IndexOutOfRangeException
   at Lucene.Net.Index.IndexWriter.HandleMergeException(System.Exception, OneMerge)
   at Lucene.Net.Index.IndexWriter.Merge(OneMerge)
   at Lucene.Net.Index.ConcurrentMergeScheduler+MergeThread.Run()

Exception Info: Lucene.Net.Index.MergePolicy+MergeException
   at Lucene.Net.Index.ConcurrentMergeScheduler.HandleMergeException(System.Exception)
   at Lucene.Net.Index.ConcurrentMergeScheduler+MergeThread.Run()
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Threading.ThreadHelper.ThreadStart()

.

Faulting application name: w3wp.exe, version: 10.0.14393.0, time stamp: 0x57899b8a
Faulting module name: KERNELBASE.dll, version: 10.0.14393.0, time stamp: 0x57899809
Exception code: 0xe0434352
Fault offset: 0x0000000000017788
Faulting process id: 0x1840
Faulting application start time: 0x01d27de3c8a59141
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Windows\System32\KERNELBASE.dll
Report Id: b8c443b9-7658-47b3-ae17-40d304a55c82
Faulting package full name: 
Faulting package-relative application ID: 

.

An unhandled exception occurred and the process was terminated.

Application ID: /LM/W3SVC/25/ROOT

Process ID: 6208

Exception: Lucene.Net.Index.MergePolicy+MergeException

Message: Exception of type 'Lucene.Net.Index.MergePolicy+MergeException' was thrown.

StackTrace:    at Lucene.Net.Index.ConcurrentMergeScheduler.HandleMergeException(Exception exc)
   at Lucene.Net.Index.ConcurrentMergeScheduler.MergeThread.Run()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

InnerException: System.IndexOutOfRangeException

Message: Index was outside the bounds of the array.

StackTrace:    at Lucene.Net.Index.IndexWriter.HandleMergeException(Exception t, OneMerge merge)
   at Lucene.Net.Index.IndexWriter.Merge(OneMerge merge)
   at Lucene.Net.Index.ConcurrentMergeScheduler.MergeThread.Run()