Bug: Identical rows in members list export

[dwanjuki]

Describe the bug
The Members List export CSV file contains some duplicate rows if more than two iterations are required to process all the members. Sites with 4000+ members affected.

To Reproduce
Steps to reproduce the behavior:

1. Filter pmpro_set_max_user_per_export_loop so that the maximum users per export loop is less than half your member count.
2. Export the Members List CSV.
3. Sort your CSV file by email or id columns.
4. Observe that identical rows exist for some members.

Screenshots
Export from a test site with 3 members and pmpro_set_max_user_per_export_loop set to 1.
Row 5 is a duplicate of row 4.

Benchmark log from the above export:

PMPRO_BENCHMARK - Total records to process: 3
PMPRO_BENCHMARK - Will process 3 iterations of max 1 records per iteration.
PMPRO_BENCHMARK - For iteration #1 of 3 - Records processed: 1
PMPRO_BENCHMARK - For iteration #2 of 3 - Records processed: 2
PMPRO_BENCHMARK - For iteration #3 of 3 - Records processed: 1

Expected behavior
There should not be any completely identical rows in the export file.

Isolating the problem (mark completed items with an [x]):

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.

WordPress Environment

WP 6.6.2 PMPro 3.1.4