It's because the objects are hitting. When you add the limbs it makes the collision box huge, which in turn, makes the objects collide.
sync on:sync rate 0:hide mouse
make object sphere 1,30:position object 1,0,0,0:calculate object bounds 1//player
make object cube 2,10:scale object 2,600,1,600:position object 2,50,-1,30 //ground
make object cube 3,10:color object 3, rgb (255,0,0):position object 3,10,0,90:calculate object bounds 3 //sword
`make object sphere 9999,10
`make mesh from object 1,9999
`delete object 9999
`add limb 1,1,1
`offset limb 1,1,0,0,500
`hide limb 1,1
`add limb 1,2,1
`offset limb 1,2,0,-50,0
`delete mesh 1
`hide limb 1,2
health#=100 //player health
inv#=0 //inventory
enemyhp#=100 //enemy health
do
if object exist(3)=1 then text 0,0,"Object 3 Exists!"
position camera object position x(1),object position y(1),object position z(1) // makes the camera
if keystate(17)=1 then move object 1,.3
if keystate(31)=1 then move object 1,-.3
if keystate(30)=1 then move object left 1,.3
if keystate(32)=1 then move object right 1,.3
if object exist(1)=1 and object exist(3)=1
if object collision(1,3)=1
inc inv#,1
delete object 3
endif
endif
if keystate(18)=1 and inv#=1
make object cube 4,10
fix object pivot 4
position object 4,0,-7,15
lock object on 4
inc inv#+1
endif
if keystate(18)=1 and inv#=2 then delete object 4
dec inv#-1
CAMY#=CAMY#+MOUSEMOVEX()*.1
CAMX#=CAMX#+MOUSEMOVEY()*.1
IF CAMX#>90 AND CAMX#<135 THEN CAMX#=90
IF CAMX#>270 AND CAMX#<225 THEN CAMX#=90
YROTATE CAMERA CAMY#
XROTATE CAMERA CAMX#
YROTATE OBJECT 1,CAMY#
XROTATE OBJECT 1,CAMX#
sync
loop
You also had some typos I fixed. Good luck with whatever it is your doing.
DBPro, limited by the programmer.