Oviraptor and Scansoriopteryx. Are they closely related?

Not in the LRT.
Nevertheless, Ma et al. 2020 tested these two disparate clades together, as if they were both members of the clade Pennaraptora (Foth, Tischlinger and Rauhut 2014).

Pennaraptora: the most recent common ancestor of Oviraptor philoceratops, Deinonychus antirrhopus, and Passer domesticus (the house sparrow), and all descendants thereof. Both Oviraptor and Scansoriopteryx are members of the Theropoda and the Compsognathidae in the LRT. Pennaraptora is a junior synonym for Compsognathidae (= Compsognathus and all descendants) in the LRT (Fig. 1). Pennaraptora is also a junior synonym for Coelurosauria which includes compsognathids, tyrannosaurs, ornithomimosaurs, and maniraptorans; + birds.

The Solnhofen bird described by Foth, Tischlinger and Rauhut 2014 is the almost headless 11th specimen, privately owned (Fig 2). It nests with Early Cretaceous Sapeornis in the LRT.

Here,
in the large reptile tree (LRT, 2201 taxa, Fig 1) oviraptorids share a clade with therizinosaurs. Basal taxa include the CNJ7 specimen attributed to Compsognathus, Sinosauropteryx, Juravenator and Masiakasaurus.

At a different node
in the LRT scansoriopterygids like Scansoriopteryx, Mei and Yi are derived from the small-skulled 12th specimen of ‘Archaeopteryx’ (= 12th Solnhofen bird, also privately owned). Until all these taxa and those between oviraptorids and scansoriopterygids (= a similar taxon list) are tested by the Ma team or others, and they nest together in that analysis, the present hypothesis of interelationships (based on more taxa) should prevail. More taxa isolate convergence.

This odd lumping of oviraptors with scansoriopterygids goes back
at least as far as Maryańska, Osmólska and Wolsan 2002, who wrote, “This analysis places Oviraptorosauria within Avialae, in a sister−group relationship with Confuciusornis.” Their cladogram nested seven oviraptorids including Caudipteryx, following Avimimus and Confuciusornis in that order.

Let’s also remember to test all the Solnhofen birds
in phylogentic analysis, because they are all different from one another. Don’t assume they are all Archaeopteryx just because everyone gloms on to that famous name.

PS
Avimimus just entered the LRT basal to therizinosaurs, not oviraptorosaurs and not Confuciusornis.

References
Agnolín FL and Novas FE 2013. Avian Ancestors – A Review of the Phylogenetic Relationships of the Theropods Unenlagiidae, Microraptoria, Anchiornis and Scansoriopterygidae. SpringerBriefs in Earth System Sciences, SpringerVerlag.
Foth C, Tischlinger H and Rauhut O 2014. New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. Nature. 511 (7507): 79–82.
Ma W, Pittman M, Lautenschlager S, Meade LE and Xu X 2020. Functional morphology of the oviraptorosaurian and scansoriopterygid skull. Chapter 8 in Pittman M and Xu X (Eds), Pennaraptoran theropod dinosaurs: past progress and new frontiers, p. 229-250. New York, NY: American Museum of Natural History Library, 2020 PDF
Maryańska T, Osmólska H and Wolsan M 2002. Avialan status for Oviraptorosauria. Acta Palaeontologica Polonica 47(1):97-116.

wiki/Pennaraptora