Assignment

Hi Kelvin,
This is an expected behavior in Moodle 3.6.1 (and even some older versions), that was changed in Moodle 3.7.

At first this behavior was reported as a bug but resolved as not a bug:
https://tracker.moodle.org/browse/MDL-59577
Then an improvement was suggested, and was finally implemented in Moodle 3.7:
https://tracker.moodle.org/browse/MDL-64377

BTW, if you think that upgrading to Moodle 3.7 would solve all your problems regarding submitting assignment, think again:
https://tracker.moodle.org/browse/MDL-65391