Here's an article from Billboard from November 1983, relevant to this thread. I found it while searching an interesting website called American Radio History, where you can search Billboard magazines by topic and year.
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BILLBOARD: Nov. 12, 1983 (page 62)
ELO Breakup Near; ‘Differences’ Cited
LONDON
It seems certain that the Electric Light Orchestra is about to blow a fuse and split.
"Irreconcilable differences" are spoken of here about the band, which records for CBS-distributed Jet Records.
The disputes, which apparently came to a head during the recording of the "Secret Messages" album, are compounded by upcoming legal action by bass player Kelly Groucutt.
According to newspapers in Europe, Groucutt says he's taking action to claim 25% of the band's gross profits since 1974. He has alleged he's been paid a "hired hand" fee of around $20,000 a year during the period when the band sold more than 10 million albums worldwide.
A statement from his company, Kagee Productions Ltd., says: "Groucutt claims to have had no proper or adequate information or accounting of his substantial and significant participation and contribution to the ELO since 1974, nor to have received proper or adequate remuneration
for his appearances and performances with and services rendered to the band."
Bill Stonebridge, speaking for Kagee, says: "We know the world tours carried out successfully by the band, and the many hit records made, and Groucutt participated fully in everything. The earnings from these activities aggregate to a very large sum."
For legal reasons, Groucutt has taken action against Jeff Lynne, songwriting front man of the band, and against Bev Bevan, now drumming with Black Sabbath. Groucutt has, however, recorded a solo album for release early in 1984, on which he was assisted by Bevan. Its title: "Lights Out."
A further problem for the ELO's future is that Lynne has made it known he's reluctant to tour with the band.
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Link to article:
www.americanradiohistory.com/hd2/IDX-Business/Music/Archive-Billboard-IDX/IDX/80s/1983/BB-1983-11-12-OCR-Page-0060.pdf#search=%22elo%20split%22