It is now five years since an openly gay minister was apppointed at a Church of Scotland parish in Aberdeen, sparking an agonised debate inside the Kirk about gay clergy.

In spite of a historic vote at last year's General Assembly to allow the appointment of ministers in same-sex relationships, it is an issue still causing controversy and division.

Not only is the matter still partly unresolved - a proposed mechanism for how individual congregations could appoint a gay minister will be voted on at this year's Assembly - but the Kirk is still losing ministers, worshippers and money.

The scale of the defections should not be overstated. Around a dozen congregations out of 1400 are thought to have left or be in talks about leaving, which would tend to suggest that the Kirk has gone some way to achieving its aim of reaching a compromise acceptable to the majority. Nevertheless, the impact of those defections is disproportionate to their number. As the matter drags on, it risks sapping morale and, on a practical level, reduces the Kirk's income at a time when numbers of churchgoers have been falling as part of a long-term trend.

The departure of two Edinburgh congregations will dismay those who hoped this controversy was dying down. Not only does it come just before the General Assembly, but the pair deliver more than £300,000 between them each year into Church coffers.

It comes at a time when the Kirk has an unexpected new figurehead, Rev John Chalmers, after the moderator designate, Rev Dr Angus Morrison, unfortunately had to stand down due to ill-health. A new moderator is announced each year, at the end of October, and he or she then has seven months to prepare before taking up their first key engagement, chairing the General Assembly. Rev Chalmers will have had barely more than a month. On being announced, he commented that those within the Church "have to learn to live with our differences", but that has proved easier said than done.

Progress has been made. The General Assembly voted in 2013 to reaffirm the Kirk's traditional view on sexuality but allow individual kirk sessions to appoint a gay minister. In October, a suggested mechanism for how this might work was brought forward. It proposes that parishes will be able to appoint ministers who are in civil partnerships, but only if the Kirk Session votes by a two-thirds majority, twice, on the general principle of appointing a gay minister. If they did so, then a third vote would be held of the full congregation, to appoint a particular minister, requiring a simple majority to pass.

It means that it will be significantly harder for parishes to appoint gay ministers than straight ones, which has understandably dismayed modernisers. Even so, it does make way for gay men and women formally to become ministers. It is an exercise in tightrope walking on an issue which has thretened to tear the Kirk apart.

If it is accepted, will that draw a line at last under this debate? Many of those preparing to meet on the Mound this May will be hoping so, but it might be unwise to bet on it.