Mark 2:1 reads:
Καὶ εἰσελθὼν πάλιν εἰς Καφαρναοὺμ δι' ἡμερῶν ἠκούσθη ὅτι ἐν οἰκῳ ἐστίν.
My first reaction in reading this text was to take ἠκούσθη as an ordinary impersonal passive ("it was heard") despite the lack of agreement with εἰσελθὼν, but upon consulting BDF § 405(2), it could also be a "personal passive." But Funk expresses some doubt by saying "(personal?). BDR, on the other hand, lacks Funk's reluctance to identify it as such.
[Note: Funk more confidently cites as examples of personal passives: 1 Cor 15:12 (Χριστὸς κηρύσσεται ὅτι), Matt 3:3 (ὁ ῥηθείς), 2 Cor 3:3 (φανεροῦσθαι ὅτι), 1 John 2:19.]
The nice part about identifying ἠκούσθη as a personal passive is that it removes the anacoluthon with the earlier participle εἰσελθών, but I'm concerned how a personal passive is supposed to work with ὅτι. Does ἀκούω ever take two arguments: a personal direct object and a complement? Or, are we dealing with yet another kind of prolepsis, in which the subject of the complementizer clause ὅτι ἐν οἰκῳ ἐστίν is somehow raised into main clause, so that it can become the (implied) subject of the main verb ἠκούσθη and construe with the participle εἰσελθών?
An interesting question indeed, and one that hardly seems to be resolved with any great confidence. I'm inclined to share Funk's reluctance to see this instance as a personal passive. As for the anacoluthon, this kind of awkwardness involving a participle that ill construes with elements elsewhere in the sentence is noteworthy elsewhere in Mark; I'm thinking of
(1) Mark 5:2 καὶ ἐξελθόντος αὐτοῦ ἐκ τοῦ πλοίου εὐθὺς ὑπήντησεν αὐτῷ ἐκ τῶν μνημείων ἄνθρωπος ἐν πνεύματι ἀκαθάρτῳ, Why not ἐξελθόντι instead of the genitive absolute?
(2) Mark 6:21 Καὶ γενομένης ἡμέρας εὐκαίρου ὅτε Ἡρῴδης τοῖς γενεσίοις αὐτοῦ δεῖπνον ἐποίησεν τοῖς μεγιστᾶσιν αὐτοῦ καὶ τοῖς χιλιάρχοις καὶ τοῖς πρώτοις τῆς Γαλιλαίας, 22 καὶ εἰσελθούσης τῆς θυγατρὸς αὐτοῦ ... These genitive absolutes are awkwardly formulated in the narrative sequence, although the sense intended is intelligible enough.
(3) Mark 7:18 καὶ λέγει αὐτοῖς· οὕτως καὶ ὑμεῖς ἀσύνετοί ἐστε; οὐ νοεῖτε ὅτι πᾶν τὸ ἔξωθεν εἰσπορευόμενον εἰς τὸν ἄνθρωπον οὐ δύναται αὐτὸν κοινῶσαι 19 ὅτι οὐκ εἰσπορεύεται αὐτοῦ εἰς τὴν καρδίαν ἀλλ᾿ εἰς τὴν κοιλίαν, καὶ εἰς τὸν ἀφεδρῶνα ἐκπορεύεται, καθαρίζων πάντα τὰ βρώματα; We have had several go-rounds on καθαρίζων vs. καθαρίζον here; it's awkward any way it's construed.
At any rate, my take on the verse in question is that the sense is, "Upon his return to Capernaum, word got about that he was at home." It's awkward, but I think that εἰσελθὼν should be understood as construing with ἐν οἰκῳ ἐστίν. We can ask -- but cannot be assured of the answer -- whether the text in question represents an earlier Aramaic formulation or an earlier (pre-Marcan) formulation that the evangelist retained. That's all speculative anyway, and this is not the proper forum for that discussion. The author is unlikely to have been trained in a γυμνάσιον.