I’m Melissa, a Shopify Guru. Thanks for reaching out to us in forums. Sorry to hear the issues you are having with your POS.
In relation to the search function, we are aware of this, that it is missing in some cases. This will be resolved soon with the next app update. That should be released over the next few days. In regards to the customer contacts being deleted. It would be best to have this issue logged with our support team, that would allow for an open line of communication there, so it can be escalated and reviewed.
The escalated team will be able to take a further look and see how this can be resolved. They may ask you also to submit a feedback log. The option to Send POS logs can be located in the app by going to Store > Support > Send a report. You can then let the team know it has been sent and they can include that for you on the ticket.
Hope this information helps! You can reach out to the Guru team https://help.shopify.com/questions if you have any questions.
Have a great day!
Melissa | Shopify Guru