Program to print float in IEEE-754 only works on MARS

Question

The program receives a float (with sinple precision) and prints it in the IEEE-764 standard as follows:

1. The number itself with simple precision;
2. The number sign;
3. The exponent minus 127
4. The mantissa in hexadecimal.

        .data

zeroAsFloat: .float 0.0
symbol: .asciiz "0x"
endLine: .asciiz "\n"
positive: .asciiz "+\n"
negative: .asciiz "-\n"
hexresult:  .space  8
    
    .text
main:
    li $v0, 6
    syscall
    mfc1 $t8 $f0 #store in $t8
    #extract bit 31
    ori  $t0 $zero 0x1
    sll  $t0 $t0 31 
    and  $a0 $t0 $t8
    srl  $a0 $a0 31
    add  $t1, $zero, $a0
    beq  $a0, 0, printPositive
    bne  $a0, 0, printNegative
main2:
    #extract bits 23-30
    ori  $t0 $zero 0xFF
    sll  $t0 $t0 23
    and  $a0 $t0 $t8
    srl  $a0 $a0 23
    addi  $t3, $zero, 127
    sub $a0, $a0, $t3
    
    #print exponent
    addi $v0 $zero 1
    syscall

    li $v0, 4 
    la $a0, endLine
    syscall

    
    li $v0, 4
    la $a0, symbol
    syscall

   
    #extract bits 0-22
    
    ori  $t0 $zero 0xFFFF
    sll  $t0 $t0 7
    ori  $t0 $t0 0x7F
    and  $a0 $t0 $t8
    jal hex
    
    li $v0, 4 
    la $a0, endLine
    syscall
 
    li $v0, 10
    syscall

printPositive:
    add $t4, $zero, $a0
    li $v0, 4 
    la $a0, positive
    syscall
    beqz $ra, main2 # when $ra is zero end program else continue
    jr $ra
printNegative:
    add $t4, $zero, $a0
    li $v0, 4 
    la $a0, negative
    syscall
    beqz $ra, main2 # when $ra is zero end program else continue
    jr $ra
hex:    
    sub $sp, $sp, 24            # Push register onto stack
    sw $a0, 0($sp)
    sw $s0, 4($sp)
    sw $s1, 8($sp)
    sw $s2, 12($sp)
    sw $s3, 16($sp)
    sw $s4, 20($sp)
    move $s2, $a0               # Move a0 to s2
    li $s0, 8                   # 8 digits for hex word
    la $s3, hexresult           # Hex string set up here

hexloop:
    rol $s2, $s2, 4             # Start with leftmost digit
    and $s1, $s2, 0xf           # Mask 15 digits in s2 and place results in s1
    ble $s1, 9, hexprint        # If s1 <= 9, go to print
    add $s1, $s1, 7             # Else s1 = s1 + 7 (to get A-F)

hexprint:
    add $s1, $s1, 48            # Add 48 (30 hex) to get ascii code
    sb $s1,($s3)                # Store byte in result. s3 -> result
    add $s3, $s3, 1             # s3 = s3 + 1
    add $s0, $s0, -1            # s0 = s0 - 1
    bnez $s0, hexloop           # If s0 != 0, go to hexloop
    
    la $a0, hexresult           # display result
    li $v0, 4
    syscall

    jr $ra                      # Return

I have no idea why the program, in QTSpim, only prints the signal, while in MARS the execution is normal. Any tips? (I believe it is due to the jr in the printPositive and printNegative functions).