There are sounds (phonemes) in English that are more about the movement between two sounds than the two sounds themselves. Specifically, /aɪ/, /aʊ/, /ɔɪ/, /e/, and /o/ (KK, as usual, although the first three are the same in IPA.)
In some regional dialects and accents, the movement between the two sounds becomes shorter and shorter, sometimes becoming a single sound. For example, in the southern U.S., you will often hear the /aɪ/ sound shortened down to a single sound like /æ/.
This is usually not a problem, as long as there is no ambiguity in context. For instance, if you’re speaking to someone from the southern U.S. and they say /æ læk/, did they just say “I like …” or “I lack …”? Big difference.
For Mandarin-speaking ESL students, however, glide shortening is often an indicator that the speaker developed a habit of speaking too quickly before working on pronunciation, and/or is making the next trailing consonant sound in a Mandarin position.
For instance, in this particular example, students will tend to say ˹ㄎ˼, which is usually produced with the tongue dropping down to constrict the throat, instead of /k/, which is produced by the tongue contacting the velar area near the roof of the mouth.
In the former case, completing the motion of /aɪ/ before dropping down to ˹ㄎ˼ takes intentional effort and practice. It often doesn’t happen.
Welcome to the South.