Invalid type for parameter inputText, value: None, type: <class 'NoneType'>, valid types: <class 'str'>

hi all,
i have a test plan with about 30 tests. each test, when run in isolation, works fine. when the test plan contains all 30, the test run often errors out with either:

botocore.exceptions.ParamValidationError: Parameter validation failed:
Invalid type for parameter inputText, value: None, type: , valid types:

or

pydantic_core._pydantic_core.ValidationError: 1 validation error for TestResult
reasoning
Input should be a valid string [type=string_type, input_value=None, input_type=NoneType]
For further information visit https://errors.pydantic.dev/2.10/v/string_type

the traces files generate ok, even with the run errors out. the summary file however is not written out. re-running the eval several times would eventually complete successfully once, then errors out again.

here is an example of the type of tests in the test plan:

question_30:
steps:
- Ask the agent to build a table with the region in rows and vendors in the columns showing data traffic for 17 of January 2025.
expected_results:
- The agent returns the matrix table with region in the rows and vendor in the columns, showing the intersected data traffic
Region | Vendor1 | Vendor2 | Vendor3 | Vendor4
Central | 7229821 | 2459730 | 0 | 0
East | 0 | 4123003 | 148 | 0
North | 0 | 0 | 304 | 0
South | 0 | 2796411 | 1811676 | 0
West | 2510043 | 1356714 | 3917543 | 0
Empty | 0 | 59270 | 209 | 2019

Start by reproducing the full 30-test plan rather than an isolated test, then inspect the trace and summary generation around the TestResult.reasoning and inputText validation errors. Compare successful and failed runs to identify why None appears; done means the complete plan consistently finishes and writes its summary without either validation error.

Written by the indexing model from the issue text.