spdlog skipping debug statements

Question

I was debugging a C++ code and stumbled upon a weird behavior from spdlog, where some debug and trace statements are skipped (I haven't tried with other log levels but I suspect they would have the same problem).

Here is the code fragment in question:

spdlog::debug("About to go through all ({}) product keys", m_product_keys.size());
for(const auto& product_key : m_product_keys) {
    std::cerr << "aaaaaa" << std::endl;
    spdlog::trace("AAAAA");
    auto product_id = DataStoreImpl::buildProductID(descriptor, product_key);
    std::cerr << "bbbbb" << std::endl;
    spdlog::trace("BBBBB");
    product_ids.push_back(product_id);
    std::cerr << "ccccc" << std::endl;
    spdlog::trace("CCCCC");
    auto key_size = product_id.m_key.size();
    std::cerr << "dddd" << std::endl;
    spdlog::trace("DDDDD");
    packed_product_ids.resize(offset + key_size);
    std::cerr << "eeeeee" << std::endl;
    spdlog::trace("EEEEE");
    std::memcpy(const_cast<char*>(packed_product_ids.data() + offset),
                product_id.m_key.data(),
                 key_size);
    std::cerr << "fffff" << std::endl;
    spdlog::trace("FFFFF");
    spdlog::debug("Packing product id {}", product_id.m_key);
    offset += key_size;
    packed_product_id_sizes.push_back(key_size);
    std::cerr << "ggggg" << std::endl;
    spdlog::trace("GGGGG");
    count += 1;
}

I'm not using any custom spdlog sink. The only initialization of spdlog that I do it calling spdlog::set_pattern and spdlog::set_level at the beginning of the program, so everything is going to standard output.

With the above code, all the lines going to std::cerr are correctly printed to stderr. However spdlog::trace("DDDDD"); is skipped and doesn't appear anywhere in the log. Here is an example of output:

[000000|1] [11:22:49.790076386] [] [debug] About to go through all (1) product keys
aaaaaa
[000000|1] [11:22:49.790263651] [] [trace] AAAAA
bbbbb
[000000|1] [11:22:49.790292578] [] [trace] BBBBB
ccccc
[000000|1] [11:22:49.790381865] [] [trace] CCCCC
dddd
eeeeee
[000000|1] [11:22:49.790426474] [] [trace] EEEEE
fffff
[000000|1] [11:22:49.790616818] [] [trace] FFFFF
[000000|1] [11:22:49.790641377] [] [debug] Packing product id rec_hdr
ggggg
[000000|1] [11:22:49.790658171] [] [trace] GGGGG

If I remove the prints to std::cerr, only BBBBB, CCCCC, EEEEE, and the debug statement before the loop are printed. All the other don't get printed. An example of output:

[000000|1] [11:34:11.003675603] [] [debug] About to go through all (1) product keys
[000000|1] [11:34:11.003709340] [] [trace] BBBBB
[000000|1] [11:34:11.003712066] [] [trace] CCCCC
[000000|1] [11:34:11.003713430] [] [trace] EEEEE

My program is multi-threaded, but this code section is executed in a single thread and it's the only thread that calls spdlog.

What could cause such spdlog statements to get skipped?

I'm using g++ 8.3.0 on Debian, and spdlog 1.8.1.