Reproduction Steps:
1. On TestLink, create 2 automated test cases
2. create platform: PL1
3. create a test plan: TP
4. add PL1 to TP
5. add the 2 test cases in TP to PL1
6. On Jenkins, TestLink plugin is able to find the 2 test cases with PL1 entered into Platform field
7. On TestLink, create platform: PL2
8. add PL2 to TP
9. add the 2 test cases in TP to PL2
10. On Jenkins, TestLink plugin is not able to find the 2 test cases with PL 2 entered into Platform field
11. On TestLink, remove the test cases from PL1 in TP
12. On Jenkins, TestLink plugin is able to find the 2 test cases with PL2 entered into Platform field

Expected:
TestLink plugin should find the test cases for each Platform even if the test cases are added to multiple platforms within a test plan.

Using Python TestLink API Client, I can get the test cases added for each platform within a test plan.
i.e.
calling tl.getTestCasesForTestPlan(test_plan_id, platformid=platform_id) with each platform's ID returns the correct test cases.