In the name of Allah, the most Gracious, the most merciful
First of all, I should mention that on the whole, Sajdeh (prostration) can be considered from different aspects, and one of those aspects is related to “pronunciation” as you mentioned.
As a general Islamic rule of Salah (prayer), there are some conditions which can invalidate your Salah (prayer). One of them is relevant to the issue of Pronounciation. In other word, it is said that in case that your pronunciation is not true (which changes the meaning), as a consequence it would invalidate your Salah or Namaz.
In the above-mentioned example as you gave, i.e.:
"subhanarabial'aya" instead of "subhanarabial'ala."
Seemingly it has changed its true meaning. Since actually the letter “P” is not available in Arabic language, then it shows that apparently it has changed the meaning to the best of my knowledge.
But, may be mis-pronunciation in Mustahab parts of Salah such as Qunoot doesn't invalidate that.
And Allah knows best