I am using PS 2017 CC. My problem is with inserting Khmer language text. It would seem that there is a problem with inserting the េ vowel. It does all the subconsonants correctly and everything but this vowel it gets wrong. Sometimes it adds it when I don't type it. for example, the word បាន becomes បោន. Or the word បង្រៀន becomes បេង្រៀន. It does this even when I copy and paste text in from another source. So the result is the same whether typed direct or pasted.
I have already gone into type settings and clicked the Southeast Asia setting, which allows it to recognize the Khmer unicode.