A reachability issue has been observed in a virtual-chassis environment, where certain servers are unable to establish connections with other servers, regardless of whether they reside within the same VLAN or not. 
If a VC (virtual chassis) is configured with some members in VC mode and for other member(s) in VCF (virtual chassis fabric) mode, it may create some network reachability issue. 

To resolve this issue, ensure all member are either configured in VC or VCF.

Switch> show virtual-chassis status

Preprovisioned Virtual Chassis
Virtual Chassis ID: xxxx.xxxx.xxxx
Virtual Chassis Mode: Enabled
                        Mstr     Mixed Route Neighbor List
Member ID Status Serial No  Model     prio Role   Mode Mode ID Interface

0 (FPC 0) Prsnt  AAAAAAAAAAAA qfx5100-48s-6q 129 Master*   N VC  1 vcp-255/0/48
                                         2 vcp-255/0/50

1 (FPC 1) Prsnt  BBBBBBBBBBBB  qfx5100-48s-6q 129 Backup   N VC  0 vcp-255/0/48
                                        2 vcp-255/0/50

2 (FPC 2) Prsnt  CCCCCCCCCCCC qfx5100-48s-6q 0 Linecard     N F  0 vcp-255/0/48
                                             1 vcp-255/0/49

To resolve this issue, ensure all members are either configured in VC or VCF.
 

request virtual-chassis mode