While attempting to reduce the list of students in a chain grades table, using the letters of one of the First Name or Surname filters, a dml_exception exception is thrown with the mixedtypesqlparam value.
Please see below the error message:

ERROR: Mixed types of sql query parameters!!

More information about this error

Debug info:

Error code: mixedtypesqlparam

Stack trace:

    line 827 of /lib/dml/moodle_database.php: dml_exception thrown

    line 1075 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->fix_sql_params()

    line 1476 of /lib/dml/moodle_database.php: call to mysqli_native_moodle_database->get_records_sql()

    line 1549 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()

    line 1759 of /lib/dml/moodle_database.php: call to moodle_database->get_field_sql()

    line 1456 of /lib/tablelib.php: call to moodle_database->count_records_sql()

    line 261 of /home/moodle/repositories/published/mod/taskchain-master/report/renderer.php: call to table_sql->query_db()

    line 115 of /home/moodle/repositories/published/mod/taskchain-master/report/renderer.php: call to mod_taskchain_report_renderer->reportcontent()

    line 91 of /home/moodle/repositories/published/mod/taskchain-master/report.php: call to mod_taskchain_report_renderer->render_report()

This issue seems to come from an incompatibility between the use of question mark placeholders in the mod_taskchain_report_chaingrades_renderer::select_sql_record() method and named placeholders provided by moodle's tablelib flexible_table::get_sql_where().
The latters are merged into the chain grade generated sql query.
The rendering process is stopped in moodle_database::fix_sql_params() which does not allow the use of two different placeholder types.

No problem noticed when using the numbering pagination.

Step to reproduce in a course containing students and a working taskchain instance:
1. in the Navigation Block, under the taskchain link, click on Class reports > Chain grades
2. click on a letter of either the First Name or the Surname filter.

What you currently get is the exception message above, while we expect to see the report table filtered.