Hello !
Same problem, and find this solution :
Search force_ssl_login
in thr file /wp-content/plugins/theme-my-login/includes/class-theme-my-login.php
Find it on lines 919 and 1909
Don’t need to change it yet on line 919
replace force_ssl_login
by force_ssl_admin
on line 1909
I haven’t try all issues but seems working.