diff --git a/engine/battle/checkbattlescene.asm b/engine/battle/checkbattlescene.asm
index 5253c3c47..24d06b8c9 100644
--- a/engine/battle/checkbattlescene.asm
+++ b/engine/battle/checkbattlescene.asm
@@ -19,7 +19,7 @@ CheckBattleScene: ; 4ea44
 	and a
 	jr nz, .from_wram
 
-	ld a, $4
+	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld a, [$a60c]
 	ld c, a
diff --git a/engine/battle/core.asm b/engine/battle/core.asm
index bac39e76f..7649eba84 100644
--- a/engine/battle/core.asm
+++ b/engine/battle/core.asm
@@ -232,7 +232,7 @@ BattleTurn: ; 3c12f
 ; 3c1bf
 
 MobileFn_3c1bf: mobile
-	ld a, $5
+	ld a, 5 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld hl, $a89b ; s5_a89b
 	inc [hl]
diff --git a/engine/billspc.asm b/engine/billspc.asm
index f94f495c6..3d1177f83 100755
--- a/engine/billspc.asm
+++ b/engine/billspc.asm
@@ -2104,7 +2104,7 @@ MovePKMNWitoutMail_InsertMon: ; e31e7
 	ld hl, wBillsPC_BackupScrollPosition
 	add [hl]
 	ld [CurPartyMon], a
-	ld a, $1
+	ld a, BANK(sBox)
 	call GetSRAMBank
 	ld hl, sBoxSpecies
 	call CopySpeciesToTemp
diff --git a/engine/mail_2.asm b/engine/mail_2.asm
index d66bbbbd7..886ee6e6e 100755
--- a/engine/mail_2.asm
+++ b/engine/mail_2.asm
@@ -69,7 +69,7 @@ ReadAnyMail: ; b9237
 	ld h, d
 	ld l, e
 	push hl
-	ld a, $0
+	ld a, BANK(sPartyMail)
 	call GetSRAMBank
 	ld de, sPartyMon1MailAuthorID - sPartyMon1Mail
 	add hl, de
diff --git a/engine/menu.asm b/engine/menu.asm
index e5a5ed6c9..83ee69373 100755
--- a/engine/menu.asm
+++ b/engine/menu.asm
@@ -730,7 +730,7 @@ Function24423: ; 24423
 	ld a, [VramState]
 	bit 0, a
 	ret z
-	xor a
+	xor a ; effectively ld a, BANK(sScratch)
 	call GetSRAMBank
 	hlcoord 0, 0
 	ld de, sScratch
@@ -738,7 +738,7 @@ Function24423: ; 24423
 	call CopyBytes
 	call CloseSRAM
 	call OverworldTextModeSwitch
-	xor a
+	xor a ; effectively ld a, BANK(sScratch)
 	call GetSRAMBank
 	ld hl, sScratch
 	decoord 0, 0
diff --git a/engine/mon_stats.asm b/engine/mon_stats.asm
index a3039eefd..dbaf635bb 100644
--- a/engine/mon_stats.asm
+++ b/engine/mon_stats.asm
@@ -174,7 +174,7 @@ GetGender: ; 50bdd
 ; sBoxMon data is read directly from SRAM.
 	ld a, [MonType]
 	cp BOXMON
-	ld a, 1
+	ld a, BANK(sBox)
 	call z, GetSRAMBank
 
 ; Attack DV
diff --git a/engine/mystery_gift.asm b/engine/mystery_gift.asm
index 67ce10168..9a8c41f91 100755
--- a/engine/mystery_gift.asm
+++ b/engine/mystery_gift.asm
@@ -1561,7 +1561,7 @@ Function10578c: ; 10578c (41:578c)
 	ld a, [sCrystalData + 0]
 	ld [de], a
 	inc de
-	ld a, $4
+	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld hl, $a603
 	ld bc, $8
diff --git a/engine/routines/emptyallsrambanks.asm b/engine/routines/emptyallsrambanks.asm
index aa4b28e0d..8b060f3ef 100644
--- a/engine/routines/emptyallsrambanks.asm
+++ b/engine/routines/emptyallsrambanks.asm
@@ -1,11 +1,11 @@
 EmptyAllSRAMBanks: ; 4cf1f
-	ld a, $0
+	ld a, 0
 	call .EmptyBank
-	ld a, $1
+	ld a, 1
 	call .EmptyBank
-	ld a, $2
+	ld a, 2
 	call .EmptyBank
-	ld a, $3
+	ld a, 3
 	call .EmptyBank
 	ret
 
diff --git a/engine/rtc.asm b/engine/rtc.asm
index dc49a9630..bed0fcda4 100755
--- a/engine/rtc.asm
+++ b/engine/rtc.asm
@@ -146,7 +146,7 @@ Function140ae: ; 140ae
 	farcall ClearDailyTimers
 	farcall Function170923
 ; mobile
-	ld a, $5
+	ld a, 5 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld a, [$aa8c]
 	inc a
diff --git a/engine/save.asm b/engine/save.asm
index af24b4d2f..a869d903e 100644
--- a/engine/save.asm
+++ b/engine/save.asm
@@ -418,7 +418,7 @@ EraseHallOfFame: ; 14d06
 Function14d18: ; 14d18
 ; XXX
 ; copy .Data to SRA4:a007
-	ld a, $4
+	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld hl, .Data
 	ld de, $a007
@@ -454,7 +454,7 @@ SaveData: ; 14d68
 
 Function14d6c: ; 14d6c
 ; XXX
-	ld a, $4
+	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld a, [$a60b]
 	ld b, $0
@@ -471,7 +471,7 @@ Function14d6c: ; 14d6c
 
 Function14d83: ; 14d83
 ; XXX
-	ld a, $4
+	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	xor a
 	ld [$a60c], a
@@ -482,7 +482,7 @@ Function14d83: ; 14d83
 
 Function14d93: ; 14d93
 ; XXX
-	ld a, $7
+	ld a, 7 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	xor a
 	ld [$a000], a