The technician should be most concerned about data integrity and security. If information on the local database server was changed during a file transfer to a remote server, it could indicate that unauthorized access or modifications were made to the data. It could also indicate a failure in the file transfer process, which could result in data loss or corruption. The technician should investigate the cause of the changes and take steps to prevent it from happening again in the future. Additionally, they should verify the integrity of the data and restore it from a backup if necessary to ensure that the correct and complete data is available. The technician should also take appropriate actions such as notifying the system administrator and management of the incident, and following the incident management process to minimize the damage caused by the incident.

When a user is unable to perform a reverse DNS lookup of an IP address to a hostname, the missing DNS record type is the PTR (Pointer) record. Here's what you need to know:
PTR (Pointer) Record:
The PTR record maps an IP address to a hostname (reverse DNS lookup).
It is used to resolve IP addresses back to domain names.
For example, if you have an IP address (e.g., 192.168.1.10), the PTR record would provide the corresponding hostname (e.g., server.example.com).

A firewall is a device or software that filters and controls the incoming and outgoing network traffic based on predefined rules. A firewall can block ICMP packets, which are used for ping and other diagnostic tools. If the workstation has a firewall enabled, it may not respond to the ICMP sweep and appear as offline. The engineer should check the firewall settings on the workstation and allow ICMP traffic if needed.

Throughput is the actual amount of data that can be transferred over a network in a given time. Throughput can be affected by various factors such as congestion, interference, errors, or hardware limitations. If the throughput is lower than the configured internet connection speed, it can cause a significant delay in data transmission. The ISP should check the throughput and identify the source of the problem.

802.11 ax is the latest wireless standard that operates in both the 2.4GHz and the 5GHz bands. It offers higher throughput, lower latency, and improved efficiency compared to previous standards. It also uses technologies such as OFDMA and MU-MIMO to reduce interference and increase capacity in dense environments. Therefore, 802.11 ax is the best choice for a wireless network in an office building with high saturation on both bands.
Reference
Part 3 of current page talks about the benefits of 802.11 ax and how it improves network performance in congested areas1.
CompTIA Network+ N10-008 Exam Cram covers the wireless standards and their characteristics in Chapter 5. It also provides practice questions and explanations for the exam.