Answered by Shaykh Faraz Rabbani
What should I do if not if on a journey right for shortening prayers? (Such as one not being sure if all the conditions are fulfilled?)

The person has only two choices: (a) they are travelers; (b) they are not. They should assess their situation and use their reasoned judgment either way. This is all they are accountable for.
Wassalam,
Faraz.