Is the port on the switch a Gigabit port? If so, the B5-Lite should be negotiating to a Gig (1000Full). In which case you should check the port on the switch, check/replace the ends of the cable, check the cable then check the B5-Lite’s port. In that order because it’s probably easiest to check in that order.
Either way I would check the preceding stuff because you shouldn’t be seeing that kind of packet loss.
If the switch is only able to do 100Full then go ahead and try 100Full, but be aware, if there is a cable problem or a problem with either port you may have to reset the B5-Lite to get it to come back up, or fix the issue so that the B5-Lite can negotiate to 100Full.
If none of the other stuff helps, answering these questions might help us to help you:
What kind of switch do you have?
How long is the cable between the switch and the B5-Lite?
Do you have other things plugged into the switch? Are they having any issues?
What kind of cable is running between the B5-Lite and the Switch?
Is there any high power radios or other electrical equipment that the cable is ran by?
Where are you pinging to when you do the ping?
Is the radio reporting a High PER rate?
Does pinging one side of the link have a higher or lower rate of loss then the other?
Can you try pinging from both sides of the link?
Have you tried pinging a device that is not a radio? (computer on the other end of the link, router, other managed device)