The videos are generally very correct. There might just be a small error here or there but Sunquan has a very good grasp of the language. He also participates in the reguar IRC chats on mondays.
Vrelat is an easy word to get wrong since most verbs either end in a consonant plus the ending
-at or they end in a vowel plus the ending
-lat. So when you see the word vrelat you immediately think it should be
vre-lat since 99% of verbs follow the normal rule. However in this case it just happens to be that the stem of the verb ends in an
/l/ which means that it should actually be
vrel-at. Because of this we generally add the past tense of the verb in the vocabulary (
http://wiki.dothraki.org/dothraki/Vocabulary#vrelat) so that it's possible to identify the situations where the verb-stem actually ends in an /l/.