Theory

Other sounds that cause problems are as below:

U:
U in Spanish sounds like the U in PUT.
So words that need the U sound as in UNIFORM and BUS are mispronounced. UNIFORM and PUT would have the same U sound.
BUS and PUT would also have the same U sound.

Double consonants in Spanish are emphasised:
This means that words like BUTTER, RUBBER and SORRY would have strong T,B and R sounds, as they would in Spanish, but in English they have a much weaker sound.

Z and TH:
In Spanish, Z sounds like TH, but in English, Z sounds like S.
This causes confusion because Spanish speakers pronounce the English Z as TH.
For example:
Zoo should be pronounced as SOO, but Spanish speakers say THOO.

W and B:
The sound of The English W does not exist in Spanish, and the English V sounds like B in Spain.
So, Spanish speakers tend to say GWOOD instead of WOOD and BERY instead of VERY.

Y AND J:
Y,J and H have very similar sounds in Spanish but are very different in English.
This is why Spanish speakers often confuse MAYOR and MAJOR and JAM and HAM.

SK and KS:
The combination SK and KS are not the same in Spanish as in English.
This is why the English ASK is sometimes pronounced AKS by Spanish speakers.

M and N:
The sounds for M and N are very similar in Spanish, which is why in Spain, ADAM is often pronounced ADAN, and FRON is used instead of the English FROM.

Verb ED endings:
The elements discussed above all add up to mean that many Spanish speakers do not pronounce the ED endings on regular verbs in the past.
This makes it difficult to understand exactly what is being said.