Ran into a save-break after updating from RC5 to RC6, which the debug logs suggested was stelnet-related. After reverting to RC5 and uninstalling stelnet from that save, then patching to RC6, the save loaded just fine. Additionally, after patching to RC6, it was possible to re-enable Stellar Networks and continue on with the save as normal, so this is probably a low-priority thing to patch.
This save has a bunch of other mods running, so I couldn't possibly say whether it's a conflict with some other mod and RC6, or just stelnet + RC6. Here's the debugging information from trying to open the save with stelnet enabled and patched to RC6:
---- Debugging information ----
cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message : com.fs.starfarer.loading.specs.privatesuper
class : stelnet.filter.ShipHullIsHull
required-type : stelnet.filter.ShipHullIsHull
converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
line number : 805471
class[1] : java.util.LinkedHashSet
converter-type[1] : com.thoughtworks.xstream.converters.collections.CollectionConverter
class[2] : stelnet.filter.LogicalOr
class[3] : stelnet.board.query.Query
class[4] : stelnet.board.query.QueryManager
class[5] : stelnet.board.query.QueryState
class[6] : stelnet.board.query.QueryBoard
class[7] : java.util.ArrayList
class[8] : com.fs.util.container.repo.ObjectRepository
class[9] : com.fs.starfarer.campaign.comms.v2.IntelManager
class[10] : com.fs.starfarer.campaign.CampaignEngine
converter-type[2] : com.fs.starfarer.campaign.save.oooO
version : not available
-------------------------------
com.thoughtworks.xstream.converters.ConversionException:
---- Debugging information ----
cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message : com.fs.starfarer.loading.specs.privatesuper
class : stelnet.filter.ShipHullIsHull
required-type : stelnet.filter.ShipHullIsHull
converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
line number : 805471
class[1] : java.util.LinkedHashSet
converter-type[1] : com.thoughtworks.xstream.converters.collections.CollectionConverter
class[2] : stelnet.filter.LogicalOr
class[3] : stelnet.board.query.Query
class[4] : stelnet.board.query.QueryManager
class[5] : stelnet.board.query.QueryState
class[6] : stelnet.board.query.QueryBoard
class[7] : java.util.ArrayList
class[8] : com.fs.util.container.repo.ObjectRepository
class[9] : com.fs.starfarer.campaign.comms.v2.IntelManager
class[10] : com.fs.starfarer.campaign.CampaignEngine
converter-type[2] : com.fs.starfarer.campaign.save.oooO
version : not available
Hopefully it helps! And thank you for the work you do on Stellar Networks, it's an enormously useful set of features