Much about the TAM system of Palenquero is poorly understood (see Schwegler & Green (2007: 275 section 1.1.) for some of the pertinent issues). The common progressive marker ta is not generally used with stative verbs (thus *i ta kelé bae 'I want to go' is always rendered as i kelé bae).
Particularly troublesome in terms of analysis is the presence of the preverbal element a- (which may or may not have morphemic status, as its function or role is unclear). Schwegler & Green (2007: 275) make this point about it in the section on Statives without past reference (slightly edited here to bring it in line with bibliographic and other practices of this Atlas):
Statives with non-past reference are expressed in two ways: (a) with the bare verb stem ( __ + V), or (b) with a + the bare verb stem (a + V).
Patiño (1983: 123) believes that the preverbal particle a in a + V is devoid of any semantic function, and that constructions (a) and (b) are, therefore, in free alternation (cf.  to  below, where polé and a polé appear to have identical meanings). To date, no plausible alternative explanation has been offered, but the suspicion persists that this a does hold a hitherto unidentified function (see now Moñino 1999).
(1) i ___ polé yebá kuenta nu.
1SG can figure account NEG
‘I cannot calculate (this).’
(2) suto a- polé ta arí- ndo no.
1PL ? can PROG laugh PROG NEG
‘We can’t be laughing.’
It has been argued (e.g.Patiño (1983: 122), Dieck (2002)) that predicate negation structures, relative clauses, and a few other environments strongly favour the omission of preverbal a. My own corpus attests to a similar behavior of a in these environments. The correlation between morphosyntactic environment and presence or absence of certain preverbal markers has only heightened our suspicion that a indeed carries a yet unidentified functional role.
Source: Schwegler and Green 2007: 276