How long surprise last?

Mobile feat vs Sentinel feat

Astonishing Raphael,
Yes, Mobile Feat don’t provoke OA but sometimes could be tricky because Sentinel feat could hit a Mobile Feat character with a reaction (and not a OA).

I try an example:
Gord the Monk (Mobile Feat)
Konan the Fighter (Sentinel Feat)
Sonja the Paladin (no Feat)

In his turn Gord try to attack Konan with a unarmed strike, and after moves to hit Sonja, (near 5 feet from Konan) he don’t provoke OA from Konan (thanks to Mobile feat 3rd bullet point VS Sentinel feat 2nd bullet point), but Gord can be hit by Konan as a reaction (Sentinel feat 3nd bullet point).

I understand, could be boggy and the last word is always from your DM (or from Master Jeremy)