Why isn't the nozzle temperature gradually increasing during print as per G-code?

[riki]

I'm encountering an issue where I'm trying to incrementally increase the nozzle temperature from 190°C to 250°C during a print using G-code, but the temperature isn't rising as expected. Here's my G-code:

M221 T0 S100.00
T0
M104 S185
M140 S60
M190 S60
M109 S190
M572 D0 S0.09
M572 D1 S0.09
G21
G90
M82
M107
G28
G1 Z0 F500
G92 E0
G1 Z0.2 F400
G1 X60 Y-2 F800
G1 X140 Y-2 E12 F200
G1 Z5 E15 F200
G92 E0
G1 F9000.0
M117 Printing...
M1001
M106 S0
G1 F8000 X40 Y120 Z0.4 E0
G1 F3000 E0.8
G1 F8000 X40 Y120 Z0.2 E0
M104 S250
G1 F48 X290 Y120 Z0.2 E1.632653
G1 F3000 E-0.8
G1 F8000 X290 Y120 Z0.4 E0
M221 T0 S100
M104 S0
M140 S0
M107
G91
G1 E-1 F300
G1 Z+0.5 E-5 Y-20 F9000.00
G28 X0 U0
M84
G90


The goal is to have the nozzle temperature slowly increase to 250°C while the `G1 F48` command is running. However, by the end of the print, it seems the nozzle temperature hasn't increased. I understand that `M104` is an asynchronous command, and I've designed it this way to allow the temperature to rise during the slow movement of the print.

Has anyone faced a similar issue or knows what might be going wrong here? Any advice on how to ensure the nozzle reaches the desired temperature during the print would be greatly appreciated.

Thank you in advance for your help!