NAV 2017 web client rendering problem

Hi,

We have a custom form that contains a lookup field, a grid, and a few other fields. When a user selects an ID in the lookup, the grid populates with corresponding records and the other fields on the form populate based on the row selected in the grid. This has all worked fine in the past.

With NAV 2017, we are having a problem with how the form is rendering after the user selects an ID. When an ID is selected, one of the additional fields on the form disappears entirely. I have identified the code that is causing the problem, but don't know what is wrong with it or how to rewrite it so that it works in both the Windows and web clients. Code is below.

Rec.RESET;
Rec.SETFILTER("ID Field", '=%1', ID);
If Rec.FIND('-') THEN BEGIN
END;
CurrPage.UPDATE(TRUE);

It is the Rec.FIND('-') that seems to be causing the rendering problem. Is there any known solution to this problem or does anyone know an alternate way to filter the records shown in a grid on a form that might work around this issue?

Cheers,
-Van