1 Peter 5:2 (Textual Issues)

NWT 1984: "Shepherd the flock of God in YOUR care, not under compulsion, but willingly; neither for love of dishonest gain, but eagerly;"

NWT 2013: Shepherd the flock of God under your care, serving as overseers, not under compulsion, but willingly before God; not for love of dishonest gain, but eagerly;

I cannot say what motivated the 1984 NWT rendering of 1 Peter 5:2, and I'm not criticizing it, but it likely was how the WH text understood the verse. When we examine this passage in different texts and translations, it comes out to be a manuscript/textual issue that probably arose for theological reasons long ago although later textual critics might have excluded the reading (variant) based on other factors. For instance, see the NET Bible for details about the textual questions surrounding the verse. However, I don't think this is about a revision of the WH text, but the main issue is whether ἐπισκοποῦντες (a Greek participle) belongs in the text or not.

This present participle continued to appear in other Greek texts after WH published their work, so it wasn't a matter of this problem only coming to light later. Yet textual critics wondered whether this participle truly belonged in the text. Westcott and Hort obviously excluded it, but the 1894 Scrivener NT includes the participle.
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WH Text: ποιμανατε το εν υμιν ποιμνιον του θεου μη αναγκαστως αλλα εκουσιως μηδε αισχροκερδως αλλα προθυμως

SBLGNT: ποιμάνατε τὸ ἐν ὑμῖν ποίμνιον τοῦ θεοῦ, ἐπισκοποῦντες μὴ ἀναγκαστῶς ἀλλὰ ἑκουσίως κατὰ θεόν, μηδὲ αἰσχροκερδῶς ἀλλὰ προθύμως,

Footnotes:
ΠΕΤΡΟΥ Α΄ 5:2 ἐπισκοποῦντες Treg NIV RP] – WH
ΠΕΤΡΟΥ Α΄ 5:2 κατὰ θεόν Treg NIV] – WH RP

The Tyndale House GNT includes the participle, but has a note detailing the manuscripts that either have or omit the reading.

NA28: ποιμάνατε τὸ ἐν ὑμῖν ποίμνιον τοῦ θεοῦ ἐπισκοποῦντες μὴ ἀναγκαστῶς ἀλλ’ ἑκουσίως κατὰ θεόν, μηδὲ αἰσχροκερδῶς ἀλλὰ προθύμως,

I'm going to include what Bruce Metzger states in his textual commentary about 1 Peter 5:2: