Subdoc multiMutations failing with Key DocumentNotFoundException after cluster changes

In all of the Subdoc situational tests running againt 7.0 and 7.1, the SDK reports a DocumentNotFoundException. The subdoc ops are mutliLookup and subMultiMutation, and they both fail with DocumentNotFoundException.

Here's an example of a failing subdoc test:
http://sdkqe-testresults.couchbase.com.s3.amazonaws.com/SDK-SDK/CB-7.1.0-2549-enterprise/RSTConnect-SUBDOC/06-08-22/059040/a99dfb40d50bb667f05cc310010dedf2-SD.html
The AggregateExceptions are all wrapped DocumentNotFoundExceptions.

With logs: SdkdConsole.log.zip

In the test we're dropping all traffic to the cluster ports (with iptables) and then re-enabling it. In the past the SDK would reconnect after the ports are allowed again and would have only successful subdoc ops, but now there are continual DocumentNotFoundException for the rest of the test.

Bug change:
I've narrowed down the bug to this change NCBC-3203 (51f3f01079b6103e1bdfebd0704d6272841f182b). The test was passing before this.