[MSX2] Dragon Slayer: The Legend of Heroes - Speed issue during the intro

[wwark]

Version of RBF : [MSX1_20230619_test.rbf]
Floppy sha1sum (program disk) : 278a012c211b75fb428bb27eef11851ce3f2fa0f Dragon Slayer - The Legend of Heroes (1990)(Nihon Falcom)(Japan)(MSX2)(Program Disk).dsk

Description of the issue:
At the start of the core with this floppy inserted, the intro starts but the texts displayed are quite slow. I checked YT video like this one https://www.youtube.com/watch?v=Kjt_-UTPw78 and we saw the texts is displayed very quickly in comparaison of the core.

After some times, the music stops but the intro is not finished and the texts start to displayed at the speed of the YT video and no more music until the start screen.

Thanks.

[GuerreroNinja]

Confirmed with other dumps of Dragon Slayer 6, the slow letters bug show on all of them. Tested with Philips NMS 8240 and Sony HB-F1XDmk2 definitions