Is there a major translation error in MN 10? I have noticed the following translation in MN10:

And again, monks, a monk, when he is walking, comprehends, ‘I am walking’; or when he is standing still, comprehends, ‘I am standing still’; or when he is sitting down, comprehends, ‘I am sitting down’; or when he is lying down, comprehends, ‘I am lying down.’ So that however his body is disposed he comprehends that it is like that.
https://suttacentral.net/mn10/en/horner

I find this in all translations of Ven Sujato and Ven Thanissaro's translations as well.
But when I checked the Sinhalese translations, I can't see this was translate as &quot;i am&quot;.
Furthermore, when a mendicant is walking they know: ‘I am walking.’
  
  Puna caparaṃ, bhikkhave, bhikkhu 
  gacchanto vā ‘gacchāmī’ti pajānāti


From my very little understanding of Pali, "gacchāmi" means "I am walking" because the verb conjugation -mi is only used for first person singular in present tense, hence the "I am" is optional. The subject is optional.

Similarly, "gacchasi" means "you are walking" but "you are" is optional because the verb conjugation -si is for second person singular in present tense. The subject is optional.

Similarly, "gacchāma" means "we are walking" because the conjugation -ma is for first person plural in present tense. The subject is optional.

However, for "gacchati" which means "he/she/it is walking", and "gacchanti" which means "they are walking", a subject is not optional and must be clearly specified because it is not obvious from the verb conjugation who it is referring to.

Of course, in continuing conversation, third person subject (singular or plural) may be omitted, if it was explicitly stated in the previous part of the conversation i.e. implied. At least, I guess so.

Please see here.