Lua: musintername and muspostbossname sometimes return garbage

I have a script that prints out all of the music names for each level. musname seems to return correctly, but musintername and muspostbossname either return an empty string (expected) or garbage leaking from the SOC definition (not expected).

Lua script:

for i = 1,1035
	if (mapheaderinfo[i] == nil)
		continue
	end

	print(mapheaderinfo[i].musname, mapheaderinfo[i].musintername, mapheaderinfo[i].muspostbossname)
end

Snippet of console output:

SPEC1

bably 
SPEC2


Recor
SPEC3

ue
Lev
SPEC4

reenfl
SPEC5

ect = 
SPEC6

ete.


SPEC7

peOfLe
BHZ

 = 110
SPEC1

kyboxS
SPEC2

gTitle
SPEC3

evelSe
SPEC4

l Tech
SPEC5

 Puffi
SPEC6

e
Flic
SPEC7

ck = t
CCZ

8
Reco
DHZ

Boss =
APZ1

Attack
APZ2


Flick
MAP99M

r%
GFZALT

boxSca
AGZALT

ee act
MP_WTR

leplay
MP_ICE

NextLe
ERZ2


LEVEL
MP_RAI

eOfLev
THZ1

Single
CEZ1

s

Lev
MP_AIR

Palace
MP_SUN

INTERF
THZ1

r = SK
DSZ2

5

Lev
CEZ2

NCOLOR
MP_DES

0000,9
RVZ2

N
Type
MP_DOM

del
Mu
MP_GHZ

7

Lev
MP_AIR

e = Eg
AGZ

rgroun
MP_ICE

= F7
S
MP_MED

sitNee
TUTORL

 = 2
S