Error when trying to export logs from site

If you try to export logs from site (only from site) for CSV or XLSx an error will be showed:

Output can not be buffered before instantiating table_dataformat_export_format.

Moodle 3.8+ (Build: 20191220)

The debug shows:

Stack trace:
line 1771 of /lib/tablelib.php: coding_exception thrown
line 194 of /lib/tablelib.php: call to table_dataformat_export_format->__construct()
line 178 of /lib/tablelib.php: call to flexible_table->export_class_instance()
line 516 of /report/log/classes/renderable.php: call to flexible_table->is_downloading()
line 182 of /report/log/index.php: call to report_log_renderable->download()