Hi Kathleen,
We have had similar issues with our TRBOs. We have 5 devices and use them at 4 different venues. We have had them freeze up in the middle of the transaction or just be slow like you said. So it's been frustrating to rely on them.
One thing we tried was to have a dedicated POS wifi just for the TRBO devices. Also, I found at one venue that being close to the wifi router was very important, the minute we drifted too far away, we noticed dropping connections. Make sure you only have 1 wifi connection on each device, we ran into an issue where it kept switching between public and private wifi to get the stronger signal which slowed it up.
If anyone else has the silver bullet to this issue, I'd love to hear it!
Thanks,
Grant