This study investigates sources of phonological cross-linguistic influence (CLI) at the initial stages of third language (L3) acquisition in light of the predictions of the second language (L2) Status Factor Model, the Typological Primacy Model, the Cumulative Enhancement Model, the Linguistic Proximity Model and the Scalpel Model. The productions of L3 rhotic sounds, /w/ and final obstruent devoicing, elicited in a delayed repetition task, were analysed auditorily in two groups of adolescent instructed learners with L1-German--L2-English--L3-Polish and L1-Polish--L2-English--L3-German language backgrounds. The results showed that dominant articulatory routines from the L1 play an important role in determining the source(s) of phonological CLI in the initial stages of L3 acquisition, at least in a learning constellation when L2 articulations have not been mastered yet in a consistently target-like manner. Based on loglinear and multiple correspondence analyses, the sources of phonological CLI were found in this study to vary feature-by-feature, thus giving some support to the Linguistic Proximity Model and the Scalpel Model. However, the high inter- and intra-individual variation that was found is so far not accounted for by any of the existing models.