Wrong result with deque range input

[oysstu]

The following code gives wrong results when the line to parse is assigned to a deque (code)

#include <scn/scan.h>
#include <scn/ranges.h>
#include <deque>
#include <iostream>
#include <string_view>

int main() {
    std::string_view line("123456,654321");
    
    std::deque<char> dq;
    dq.assign(line.begin(), line.end());
    
    scn::ranges::subrange range(dq.begin(), dq.end());

    auto result = scn::scan<int, int>(range, "{},{}");
    if(result) {
        auto [v0, v1] = result->values();
        std::cout << "Result: " << v0 << ", " << v1 << "\n";
    } else {
        std::cout << "Failed: " << result.error().msg() << "\n";
    }
}

Which prints Result: 123456, 6. Adding a space after the comma in both the format string and input line yields the expected result. I guess that takes a different code path. I've also hit many cases of parsing result being EOF or "Argument list not exhausted", but these are seemingly random and I haven't found a consistent way to reproduce them.