SQL Server Internal Memory Error I am using SQL Server 2016 Standard Edition that shows the following errors on DBCC CHECKDB and also on updating statistics. 

 Version: Microsoft SQL Server 2016 (SP2-CU2) (KB4340355) - 13.0.5153.0 (X64) 
 Jun 28 2018 17:24:28 Copyright (c) Microsoft Corporation Standard Edition 
 (64-bit) on Windows Server 2012 R2 Standard 6.3 &lt;X64&gt; (Build 9600: ) (Hypervisor)


MAX Memory set at 215GB from 244GB x1e.2xlarge AWS EC2
There are around 260 databases.
Locked Pages in Memory is on.
Page File size is 8GB.

Memory optimized tables that uses less than 10GB of memory.


  Failed to reserve pages: FAIL_PAGE_RESERVATION
  
  Error: 8645, Severity: 17, State: 1. A timeout occurred while waiting
  for memory resources to execute the query in resource pool 'internal'
  (1). Rerun the query.
  
  Error: 701, Severity: 17, State: 135. There is insufficient system
  memory in resource pool 'internal' to run this query.


After multiple errors like these, the server shutdown itself.

Page life expectancy is 1297050, no memory grants pending, doesn't appear to have any memory pressure.

Any ideas on this issue?
You state:


  MAX Memory set at 215GB


As @Shanky stated in the comments, set max server memory (MB) to 128 GB via sp_configure as that's the limit of usable memory for SQL Server Standard Edition.

I've run into a similar issue with SQL Server Express edition when I had it set higher than it's usable limit.