We actually just noticed tail drops on our 15.1R5.5 on a stack of ex4550's , which appears to have started directly after the upgrade to 15.1R5.5. We increased the uplink speed to 40gbps to see if perhaps some microbursts are the issue, however the tail dropped packets persist.
Did you ever get a resolution to this issue?
Flow control is not enabled on this link, or at least the under
Link-level type: Ethernet, MTU: 9216, Speed: 40Gbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 1bps