Subtitles disappearing while watching on my Android Tab

Hi:

When watching kdramas on my Samsung Android Tab, the subtitles disappear for large portions of time, often reappearing only to disappear again. I watch the subs in English and it makes it difficult to follow the plot. I’ve observed that this problem disappears if I watch it on my laptop, but it is inconvenient for me to take my laptop everywhere and I bought the Tab specifically to watch dramas on viki!

Is there anyway to fix this? It happened when I was watching episodes of Gold Rainbow and Pretty Man - if this helps.

Please advise on this. Thanks.