FreeDOS works very slow, but by hitting any key rapidly FreeDOS works faster.

I wondered where to post this, but since this problem occurs from boot time, I think the kernel has a problem, so I'm posting it here.

I'm using FreeDOS on a laptop computer, TOSHIBA Dynabook 660CDT . This computer has Pentium 150MHz processor.

FreeDOS was installed by downloading the "FreeDOS 1.3 LegacyCD" from the official site's download page and booting from the FDD.

I replaced its HDD to SSD by converting mSATA SSD to IDE, and I installed Windows 95 and FreeDOS to it. Also, I installed GNU GRUB bootloader to be able to switch between those operating systems at will.
GRUB bootloader and Windows 95 work well, but I found FreeDOS works very slow. FreeDOS allows the user to switch between driver loading settings at startup, but it took 10 seconds for all of the choices to appear and become operational. Additionaly, when I ran MEM command, it took more than 1 minute to display memory information.

At first, I thought the problem was caused by the dual boot configuration by using GRUB. So I booted FreeDOS from a floppy disk with FreeDOS installed. But even so, FreeDOS also works very slow.

This problem does not seem to be some driver issue, as it is occurring at the time of the config selection menu which should be before any driver is loaded.
The computer will also have a power saving mode that reduces the CPU clock, but of course that is disabled in the BIOS settings.

After a while of trial and error, I noticed something very odd.
I was so frustrated with how slow it was running that I hit the BackSpace key repeatedly during startup. Then oddly enough, FreeDOS ran as fast as it did when installed in a virtual machine.
Not only the BackSpace key, but any key on the keyboard, except for modifier keys such as Shift and Ctrl, FreeDOS runs fast no matter which key is hit repeatedly.
Even that MEM command could display information in an instant when I hit any key repeatedly.

Although hitting a key repeatedly makes it run faster, this is very inconvenient because I have to hit the key repeatedly every time I want to execute some command.

I am not familiar with the core of DOS, isn't this a bug in the kernel?