This might not be a bug, but it does not appear to be in the patch notes for the latest update, so there is no sign that this is NOT a bug.
As of 1.4.1, Guards are no longer receiving any increase in shield strength based on synergy level. The difference is at least 4k on an Inquisitor S; at max synergy, shield strength was at least 26k, and is now only 22k. Part of the reason I think this is likely a bug is that every other ship role still gets that increase in shield strength. For that matter, no other role has lost any synergy level-based increases. This discrepancy shows up anywhere you can view ship stats, as well as in-game. All of the other stats that are affected by synergy level still receive their increases on Guards.
For those who might suggest this is not really a problem due to the recent increase in Guard shield resistances, Guards still have lower base shield resistances than all other roles. It was -30 until the increase, but is still -20 in comparison to most other roles. (Command and Tacklers have +10 to all shield resistances in comparison to most other roles.)