Disproportionation reaction of dimeric sulphur monochloride
Compiling my comments into an answer, sulfur monohalide disproportionate to sulfur dihalide and/or sulfur tetrahalide and elemental sulfur.
Wikipedia has the reaction:
$$\ce{2S2F2 -&gt;[180 ^\circ C] SF4 + 3S}$$
Also, there is a reaction scheme from a 1974 entry1 which indicates formation of octasulfur and sulfur difluoride as sideproduct.
$$\ce{12S2F2 -&gt; 3S8 + 8SF4}$$
$$\ce{8S2F2 -&gt; S8 + 8SF2}$$
It also further noted that this disproportionation reaction is useful in the synthesis sulfur tetrafluoride and the decomposition of two moles of $\ce{S2F2}$ into one mole of $\ce{SF4}$ and sulfur yields $\pu{\Delta H^\circ = -24.6 kcal/mole}$.
Furthermore, sulfur difluoride may disproportionate to sulfur tetrafluoride and sulfur or some other oligomer/polymer of sulfur or back to sulfur monofluoride or isomerize to various sulfur compounds like $\ce{FSSF}$,  $\ce{SSF2}$ or $\ce{SF3SF}$. These compounds are extremely unstable and prone to hydrolysis:
$$\ce{16SF2 -&gt; 8SF4 + 8S8}$$
$$\ce{3SF2 -&gt; SF4 + S2F2 isomers}$$
The stability of $\ce{SF2}$ can be considered thermodynamically. The decomposition of two moles of $\ce{SF2}$  to yield $\ce{SF4}$ and $\ce{S8}$(gas) is $\pu{-75.7 kcal/mole}$. Another reason for this decomposition is polymerization which forms new sulfur-fluorine bonds. Also, it is noted that $\ce{SF4}$ is thermodynamically unstable and disproportionate to sulfur hexafluoride and sulfur:
$$\ce{24SF4 -&gt; 16SF6 + S8~~~~\Delta H^\circ = -62.9 kcal/mole}$$
So, sulfur compounds in these intermediate oxidation state are found to be thermodynamically unstable and it is also influenced by its kinetic stability.
Sulfur monochloride disproportionation occurs in a similar way as noted in this patent:

Elevated temperature as used herein refers to temperatures between
about 75 and about 150C; and preferably between about 85 and about
138C. Higher temperatures can be used but the sulfur monochloride will
tend to disproportionate to form sulfur and sulfur dichloride. lf
higher amounts of sulfur in the sulfur monochloride product are not
objectionable, higher temperatures can be utilized

Notes and References

Advances in Inorganic Chemistry and Radiochemistry, Academic Press, 1974
There is a different pathway for disproportionation of selenium monochloride/bromide where it is seen to yield $\ce{SeX2}$ and $\ce{Se_{n}X2 (n =3,4)}$ unlike the general pathway you mentioned which yields $\ce{SeX4}$ and elemental selenium. See this paper for more details.