If by any chance you are using mods other than SS2, DO NOT use this mod: 'FC-HiddenCafe'. In my recent play, he crashed my game in downtown Boston and the South Boston Checkpoint, as well as other regions. After I removed it, I've played more than 30 hours without any accidents.
The mod in question allows you to access the hidden room at the top of Diamond City, in the outer area.
Incase it helps this is my load order (I cant make the Add Ons higher for some reason. I guess * means enabled and without it means I dont have it enabled?
*unofficial fallout 4 patch.esp
*hudframework.esm
*workshopframework.esm
ss2.esm
ss2_xpac_chapter2.esm
*nb_budgetlimitremover.esl
*kcore's simple - clinic beds and medbay.esl
*factionpipboys.esl
*cclub - modular military backpack.esl
*armorkeywords.esm
ss2extended.esp
ss2_cityplanpack_riseofthecommonwealth.esp
*workshopplus.esp
*settlementmenumanager.esp
*weightless junk.esp
*visiblecompanionaffinity.esp
*modenclavearch38.esp
*p99.esp
*wrvr.esp
*modern firearms.esp
*militarizedminutemen.esp
*the eyes of beauty.esp
*workshopturretpack.esp
*k9tacticalharness.esp
*artilleryv6.esp
*instabell.esp
*evilviking13_minutemenmorale.esp
sophie looksmenu preset test.esp
*manufacturingextended.esp
*improved map with visible roads.esp
*nonegativeaffinity_acceleratedaffinity.esp
*beautiful female settlers v. 2.0 - non replacer.esp
*busty grrl.esp
*companion infinite ammo.esp
*companionhaircut.esp
*cheatterminal.esp
*everyonesbestfriend.esp
*aesammocraftingworkbench.esp
*sleepintimate.esp
primez military fatigues.esp
*_mdcminutemenlabcoat.esp
*nw77_vanillawavingflagpolespack.esp
*r97r colonial duster.esp
*enclave colonel uniform.esp
*spawn items.esp
*atonga's general's gear.esp
*eli_vault-tec outfits.esp
*leeenfieldno4mki.esp
*mre.esp
*vault88expansion.esp
*r97r standalone suits.esp
*survival console.esp
skkfaststartnewgame.esp
*crx_fotnk.esp
*nw77_hibernia.esp
*nw77_unionjack.esp
*nw77_flagsoftheunitedstatesmegapack.esp
*macvaultlooter.esp
*vault 76 theme - for vault-tec workshop.esp
*vault144.esp
*stronger defense.esp
*denim and leather for kate.esp
*misfitink.esp
the castle.esp
*brotherhood of steel overhaul.esp
*america rising - a tale of the enclave.esp
*modsexylingerieopt.esp
*junkwallstallonly_more_snaps.esp
*junkwalls_more_snaps.esp
coastal-cottage-04.esp
*factionbandanas.esp
*egret tours marina minuteman naval base.esp
*0oicmilitaryclutter.esp
*americarising-gearoftheenclave.esp
*food rating equalizer.esp
*_sniper_perk_expanded.esp
*__fortune_finder_leveling.esp
*clean and simple - starlight drive in startup.esp
*eli_faction housing overhaul - aio.esp
*minutemen's vertibirds workshop.esp
clean and simple - red rocket startup.esp
*sanctuaryrebuild orig p13h.esp
*minutemenrelooked.esp
*immersivedecor.esp
*more fortifications.esp
nickoverhaul.esp
*theminutemanpistolstandalone.esp
beveragestation.esp
jm-dogpatch.esp
*hopesarmory.esp
*keep radiants in commonwealth.esp
*minuteman power armor.esp
sanctuary-estates-clean-01.esp
*clean and simple - the castle startup.esp
*sanctuaryparts.esp
*ebitems.esp
*dinoshelf.esp
*creativeclutter.esp
signsofthetimesposters.esp
*decorpack.esp
*settleobjexpandpack.esp
gruffyddssignsandposters.esp
*thedawnoftheminutemen.esp
*azarholsteredweapons.esp
conquest.esp
*clean and simple - spectacle island startup.esp
*settlementcopbot.esp
wdp.esp
stonewarehousewalls.esp
skey_moreguardposts_en.esp
*3dnpc_fo4.esp
*snappy_housek.esp
sanctuary-estates-clean-bos.esp