At the FFV ending these two glitches always happened to me. the first I believe is a problem with the translation itself, but the second is suddenly in all SNes9x versions (I don't use another emulator) and all the roms I found (translated or not), what could be causing these bugs?

First question, which times are your bugs? I see strange cut at 0:23, but no other.

Second question, are they related to the msu patch or also experienced in unpatched spc version?

Third... I cannot find your sequence in the spc endings on YouTube to compare...
https://m.youtube.com/watch?v=ZWaSER_Otj4

In the first bug the phrases are repeated and mirrored at the bottom of the screen, in the second there are red artifacts in mode 7. Now watching the World of Longplay' FFV video on Youtube I found that this has to do with the SNes9x emulation (and nothing to do with the MSU-1) see at 1:56:15 and then at 2:14:15 this video to see that it has the same bugs that I mentioned:

Ah, you almost scared me that an undetected msu bug was found. I see now what you mean and have to give you bad news. There's almost nothing I can do without giving huge efforts into it, hourless debugging and so on, learning about mode7 again, trying to retrace what the author used for pointers.... ... ... where I currently have neither the time, interest, nor mood.

Is there a chance for you to contact the author and ask him to fix these bugs (in case they do not appear in original Japanese, they are caused by him).

I find it difficult, until today they did not solve that problem of sound delay at the FFVI ending.

That's an issue with the translation patch, and I'd guess it has to do with how they had to code replacing the kanji with english in the ending scroll.

It's a known bug to the translators.

It's likely not getting fixed, as it's been quite a while since the translation patch has been updated.

FFV or FFVI?

Because what I use are these:

-FFV GBA Script Port.

-FFVI Retranslated.

Erm.... this is the FFV thread, so yea, FFV.

This is the patch with the end-scroll visual glitch:
English Translation Patch by RPGe:
https://www.romhacking.net/translations/353/

FFVI is also has a bug at the the game ending and in several translations, about FFV I use this one which is based on the RPGe version but all corrected and much more complete:

http://www.romhacking.net/hacks/3687/

Patch is updated to fix sd2snes resume:
Reason is the resume $2007:04 in sd2snes which qwerty found out while working on zelda LA DX.
If you want to resume a currently played track somewhen later you make a LDA #$04 : Sta $2007

On sd2snes it takes a time to transfer the resume location, so if you immediately make a STA $2004: newTrack, the resume info might get lost.

To overcome I added this loop:
LDA #$04
STA $2007
loop41:
LDA $2000
AND #$10
BNE loop41

Conn wrote:Patch is updated to fix sd2snes resume:
Reason is the resume $2007:04 in sd2snes which qwerty found out while working on zelda LA DX.
If you want to resume a currently played track somewhen later you make a LDA #$04 : Sta $2007

On sd2snes it takes a time to transfer the resume location, so if you immediately make a STA $2004: newTrack, the resume info might get lost.

To overcome I added this loop:
LDA #$04
STA $2007
loop41:
LDA $2000
AND #$10
BNE loop41

That's it Conn!

I've downloaded and applied the fixes here;
also on Mega Man X1, X2, X3 and Zero Project,
thank you so much!!!

Synthetic Origins FFV PCM set:
https://mega.nz/file/Wd5xkKiY#QfjQqUIj8TV1JUW8QWCRi8Xf5ObSK1ZsYdH3t6u1QIg

(already added to OP)