[checkbox] Checkbox fails to generate the HTML and Tarball for a session, and loses the session.

[Summary]
After Checkbox finishes it is supposed to generate a HTML, XML and tar.xz of the test data and logs.

However after finishing the checkbox-iiotg-classic 20.04 Manual for Server test plan, Checkbox encountered an error and was only able to generate the XML file. Since the session is now closed, the test data was lost and the tests will have to be rerun.

The session was then modified to still show as "open" and the report generation was tried again but it still failed.

[Steps to reproduce]
Run Server Manual.

[Expected result]
Checkbox should properly generate the 3 test files.

[Actual result]
JSON errors prevent the generation of the HTML and tarball.

[Failure rate]
2/2 100%

[Additional information]
CID: 202109-29496
SKU:
system-manufacturer: AAEON
system-product-name: UPN-EHL01
bios-version: UNEHAM11
CPU: Intel Atom(R) x6425RE Processor @ 1.90GHz (4x)
GPU: 00:02.0 VGA compatible controller [0300]: Intel Corporation Device [8086:4571] (rev 01)
kernel-version: 5.15.0-1016-intel-iotg

[Stage]
Issue reported and logs collected at a later stage