Today if we detect concurrent modification of a snapshot repository then we mark it with `CORRUPTED_REPO_GEN` which blocks further writes to try and prevent additional damage to its contents. You can remove the marker by calling the register-repository API again, but this API will discard no-op re-registrations without taking any action. You can work around this by unregistering the repository first (which may be impossible if it's still in use for searchable snapshots) or by re-registering it with some trivial setting change (which seems hacky).

We should not consider it a no-op re-registration if the repository is currently marked with `CORRUPTED_REPO_GEN`, because doing this re-registration will re-read the repo contents and clear the corruption marker and therefore is not a no-op.
test/framework/src/main/java/org/elasticsearch/snapshots/AbstractSnapshotIntegTestCase.java
final SnapshotInfo snapshotInfoInResponse = response.getSnapshotInfo();
                    assertEquals(userMetadata, snapshotInfoInResponse.userMetadata());
                    clusterAdmin().prepareGetSnapshots(repoName).setSnapshots(snapshot).execute(l.delegateFailure((ll, getResponse) -> {
                        assertEquals(snapshotInfoInResponse, getResponse.getSnapshots().get(0));
                        ll.onResponse(response);
                    }));
                }));
        }
        for (CreateSnapshotResponse snapshotResponse : allSnapshotsDone.get()) {
            assertThat(snapshotResponse.getSnapshotInfo().state(), is(SnapshotState.SUCCESS));
        }
        logger.info("--> created {} in [{}]", snapshotNames, repoName);
        return snapshotNames;
    }
    public static void forEachFileRecursively(Path path, CheckedBiConsumer<Path, BasicFileAttributes, IOException> forEach)
        throws IOException {
        Files.walkFileTree(path, new SimpleFileVisitor<>() {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                forEach.accept(file, attrs);
                return FileVisitResult.CONTINUE;
            }
        });
    }
    public static void assertSnapshotListSorted(
        List<SnapshotInfo> snapshotInfos,
        @Nullable GetSnapshotsRequest.SortBy sort,
        SortOrder sortOrder
    ) {
        final BiConsumer<SnapshotInfo, SnapshotInfo> assertion;